TRAFFIC ACCIDENT ANALYSIS

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TRAFFIC ACCIDENT ANALYSIS Westheimer at Chimney Rock and Westheimer at Dunvale Prepared for Prepared by Klotz Associates, Inc. 1160 Dairy Ashford, Suite 500 Houston, Texas 77079

The preparation of this document was financed in part through grants from the U.S. Department of Transportation under Section 112 of the 1973 Federal Aid Highway Act and Section 8(d) of the Federal Transit Act of 1964, as amended. The contents of this document do not necessarily reflect the official views or policy of the Federal Highway Administration, U.S. Department of Transportation, Texas Department of Transportation,, Harris County, or City of Houston. Acceptance of this report does not in any way constitute a commitment on the part of any of the above agencies to participate in any development depicted therein nor does it indicate that the proposed development is environmentally acceptable in accordance with appropriate public laws.

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S ACKNOWLEDGEMENTS The authors acknowledge with deep appreciation the assistance received from individuals contacted during the course of data collection and report development. Especially helpful were Mr. Jerry Bobo, H-GAC Program Manager; Dr. Ned Levine, H-GAC Transportation Program Coordinator; and Mr. Ilyas Choudry, H-GAC Senior Transportation Engineer. The insights and experience of the H-GAC staff provided the authors with an understanding of the problems and challenges facing H-GAC in managing area planning, congestion management, and safety activities. Also, Mr. Gary Schatz, P.E., City of Houston Senior Engineer, provided valuable assistance in obtaining crash data information. Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S TABLE OF CONTENTS SECTION 1 INTRODUCTION...1-1 1.1 Study Objective and Scope...1-1 1.2 Study Methodology...1-2 SECTION 2 DATA COLLECTION... 2-1 2.1 Field Investigation...2-1 2.2 Traffic Crash Data...2-1 2.3 Traffic Counts and Signal Timing Plans...2-3 SECTION 3 EXISTING CONDITIONS...3-1 3.1 Westheimer at Chimney Rock...3-1 3.2 Westheimer at Dunvale...3-3 SECTION 4 SAFETY ANALYSIS... 4-1 4.1 Hazard Reduction Analysis...4-1 4.2 Benefit Cost Analysis...4-3 4.3 Analyses Results...4-5 4.3.1 Westheimer at Chimney Rock...4-5 4.3.2 Westheimer at Dunvale...4-9 SECTION 5 SUMMARY...5-1 APPENDICES APPENDIX A EXHIBITS APPENDIX B COLLISION DIAGRAMS APPENDIX C TXDOT HAZARD ELIMINATION PROGRAM APPENDIX D DPS ACCIDENT DATA APPENDIX E EXISTING SIGNAL TIMING DATA APPENDIX F PHOTOGRAPHS TOC-1 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S SECTION 1 INTRODUCTION H-GAC plans to develop a Transportation Safety and Hazard Elimination Program for the Houston-Galveston region to enhance traffic safety on roadways throughout the area. The program would identify and implement safety and operational improvements that would reduce the frequency and severity of traffic collisions. To assist in developing the safety program, H-GAC initiated a pilot study for crash data collection and analysis. This report documents the methodology and results of the pilot study. 1.1 Study Objective and Scope The objective of this pilot study is to demonstrate the methodology employed to conduct a traffic crash analysis. This type of analysis is necessary to identify safety problems and propose cost-effective countermeasures for a specific roadway location. The H-GAC Long-Range Planning Group identified two high-risk crash intersections to be investigated in this pilot study, Westheimer at Chimney Rock and Westheimer at Dunvale, in Houston, Texas. A location map is presented in Appendix A as Exhibit A1. The scope of this study included the following tasks: 1. Intersection Descriptions. This task included description of the two study intersections, preparation of the existing condition layouts and photographs from all directions. 2. Data Collection. For the two study intersections, data collection included obtaining traffic crash data from the City of Houston and H-GAC; and gathering any existing traffic volume data and traffic signal timing plans from the City of Houston. 1-1 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S 3. Collision Diagrams. This task included detailed review of the crash data and development of collision diagrams for each of the two intersections depicting the type, severity and frequency of crashes. 4. Hazard Reduction Analysis and Recommendations. The analysis and recommendations task included an evaluation of crash patterns and recommendations for improvements to correct various types of crashes. 5. Cost Estimation. This task included the preliminary cost estimation of the recommended improvements. 6. Benefit Cost Analysis. This task involved the benefit cost analysis for each preventable crash type following the guidelines stipulated for the Hazard Elimination Program of the Texas Department of Transportation (TxDOT). 1.2 Study Methodology The procedure used to conduct the traffic crash analyses is listed below: 1. Review the existing conditions through field visits and observations. 2. Gather recent crash data from different agencies in the region. 3. Prepare an existing condition layout of the intersection. 4. Study individual accident reports, if available, and summarize collisions on a collision diagram. 5. Review all collisions with regard to type and severity, and determine patterns or changes in collision types. 6. Identify improvements or modifications to correct particular types of crashes. 7. Perform a benefit cost analysis of potential improvements. 1-2 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S SECTION 2 DATA COLLECTION Data collected for the study intersections included the roadway and intersection geometry, traffic crash data, traffic count data, and the existing traffic signal timing plans. The following sections summarize the data collection activities. 2.1 Field Investigation A field investigation was conducted at the two study intersections on September 17, 2002 to gather existing conditions information including the intersection geometry, lane use, traffic signals and intersection related signing, pavement markings, pavement type, and adjacent land use. Photographs were taken of all traffic control devices and the intersection approaches. During the field investigation, observations of traffic were made at the intersections to identify and examine potential safety problems. 2.2 Traffic Crash Data Traffic crash data for the study intersections was gathered for the previous three year period. This type of data is the most critical information necessary to perform a traffic safety review of an intersection. Often, accurate and reliable crash data are difficult to obtain. However, there are several means available to gather this type of data, either through state and/or local officials. A brief discussion of the accident reporting process in the State of Texas is provided for background purposes. The Texas Transportation Code (Section 550.062) governs this process, which requires law enforcement agencies to report traffic crashes to the Texas Department of Public Safety (DPS) when the crash is investigated by a law enforcement 2-1 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S officer and results in injury or death of a person or damage to the property of any one person to the apparent extent of $500 or more. Local law enforcement and DPS officers forward accident reports to the DPS central office where the crash information is coded into a statewide database. These coded data are available upon request to DPS. However, there is a typical delay of at least 18 months before the crash data are available. Accident reports can also be requested and obtained from DPS when coded information is not adequate. However, more recent accident reports can be obtained from local officials. For the purposes of this study, data were obtained from both City of Houston and DPS. In order to conduct a thorough analysis of recent crash trends, it was necessary to obtain accident reports directly from the City of Houston Police Department (HPD). Upon request, HPD provided accident reports for crashes that have occurred within the last two years at the study intersections. The City of Houston Public Works and Engineering Department provided assistance in acquiring this data. Like many law enforcement agencies, HPD maintains a computer database in which all reported traffic crashes are recorded. The database system primarily serves the purpose of locating an accident report for an individual involved in a collision. The accident reports are logged by date, driver s name, and location, i.e., block number and street name. When data are needed for a particular location, as is the case in an intersection crash analysis, it is important to provide accurate block numbers and street names. Also, the search request must include various versions of street names, if they exist. The HPD search results provides a listing of crashes that have occurred at the location requested. Using the search results, the specific accident reports for the study intersections were retrieved and provided for the analysis. As part of H-GAC s effort to monitor crash trends throughout the area, H-GAC previously obtained Year 1998 and 1999 coded crash data from DPS. These data were provided by H-GAC for the analysis. 2-2 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S 2.3 Traffic Counts and Signal Timing Plans Traffic count and existing signal timing plan data are useful in the analysis and in the evaluation of future improvements and modifications. Traffic volume data for the study intersections were requested from the City of Houston for the past three years. The only applicable volume information available included 24 hour traffic volume counts taken in both directions on Westheimer near the study intersections in 1999. These data were provided by the City of Houston Traffic Management and Maintenance Branch. The traffic volumes on Westheimer were 60,689 vehicles per day west of Chimney Rock, 49,871 vehicles per day east of Chimney Rock, and 64,034 vehicles per day east of Dunvale. No turning movement data at these intersections were available. The existing signal timing plans for the study intersections were obtained from the City of Houston and are provided in Appendix E. 2-3 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S SECTION 3 EXISTING CONDITIONS The existing conditions at the study intersections are described in this section. 3.1 Westheimer at Chimney Rock The intersection of Westheimer and Chimney Rock is located approximately 1.2 miles west of the West Loop Freeway (IH-610) in west Houston, Texas (see Appendix A Exhibit A1). The existing intersection layout is shown in Appendix A as Exhibit A2. Also, photographs of the intersection are provided in Appendix F. Westheimer is an eight-lane east-west roadway serving as a principal arterial between downtown and the west Houston area. The roadway has asphalt pavement with curb and gutter drainage, 12 feet travel lanes, and a concrete raised median. There is no vertical curvature alignment along Westheimer. Both the eastbound and westbound approaches of Westheimer have straight horizontal alignment. The posted speed limit on Westheimer is 35 miles per hour. The land use along Westheimer within the study area is predominately commercial. Several driveways are located near the intersection that provides access to these businesses. Chimney Rock within the study area is a four-lane boulevard that is aligned in a northsouth direction. Chimney Rock has concrete pavement with curb and gutter drainage, 12 feet travel lanes, and a raised median. There is no vertical curvature alignment along Chimney Rock. The northbound approach to the intersection has straight horizontal alignment. However, the southbound approach has a slight horizontal curvature. The posted speed limit on Chimney Rock within the study area is 35 miles per hour. The land 3-1 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S use adjacent to Chimney Rock north of Westheimer is primarily residential, while south of Westheimer the land use consists of commercial retail developments. At the time of the field investigation, Westheimer had recently been overlaid with asphalt pavement. The asphalt pavement in the center of Westheimer had been milled, but the asphalt had yet to be applied in this area, leaving a slight drop-off in the middle of the Chimney Rock at Westheimer intersection. During the field visit, it was observed that traffic slowed considerably while crossing the intersection on Chimney Rock which caused poor traffic operations and potential rear end collisions. Because of the recent overlay, the pavement condition on Westheimer was observed to be in excellent condition. The pavement along Chimney Rock appeared to be in good condition, although there was some degradation of pavement on the northbound intersection approach at the stop line where vehicles routinely stop. The concrete handicap ramps on the southwest corner were observed to be cracked and unsmooth. The caved-in concrete appeared to be caused by heavy vehicles turning from Westheimer to Chimney Rock. The intersection is controlled by a semi-actuated traffic signal which operates within a coordinated traffic signal system along Westheimer. The traffic signal is a span-wire design application with strain pole installation. The traffic control provides for protected left turn phasing on all approaches with separate left turn bays. The left turns from Westheimer are prohibited by signage during peak weekday traffic periods. The details of the intersection geometry, traffic and pedestrian signals, pavement markings, and signs are shown on the intersection layout (see Appendix A -Exhibit A2). The signal heads were observed to be in fair condition. Several overhead lane designation and prohibition signs were observed to be faded and in poor condition. Pavement markings on Westheimer consist of reflective striping that was recently installed on the new asphalt overlay and therefore, appeared to be in excellent condition. The pavement markings on Chimney Rock also consist of reflective striping. The lane 3-2 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S designation markings and the pedestrian crosswalks and stop lines on the Chimney Rock approaches were observed to be in poor condition. A bus stop shelter on the southwest corner of the intersection was observed to marginally restrict sight distance for northbound traffic on Chimney Rock looking toward the west from the stop line. This sight distance is necessary when motorists desire to make a right turn on a red signal. The visibility restriction was evidenced by the observation that motorists drove considerably forward across the stop line near the outside travel lane of Westheimer to see traffic on Westheimer. 3.2 Westheimer at Dunvale The intersection of Westheimer and Dunvale is located approximately 3.4 miles west of the West Loop Freeway (IH-610) in west Houston, Texas (see Appendix A Exhibit A1). The existing intersection layout is shown in Appendix A as Exhibit A3 and photographs of the intersection are provided in Appendix F. Westheimer is an eight-lane east-west roadway serving as a principal arterial between downtown and the west Houston area. The roadway within the study area has asphalt pavement with curb and gutter drainage, 12 feet travel lanes, and a concrete raised median. There is no vertical curvature alignment along Westheimer. Both the eastbound and westbound approaches of Westheimer have straight horizontal alignment. The posted speed limit on Westheimer is 35 miles per hour. The land use along Westheimer within the study area is predominately commercial. Several driveways are located near the intersection providing access to these businesses. Dunvale is a four-lane undivided roadway that intersects Westheimer on the south side of the intersection. On the north side of the intersection, a three-lane driveway providing access to a K-Mart Super Center forms the fourth approach to the intersection. Dunvale and the K-Mart driveway have concrete pavement with curb and gutter drainage. There 3-3 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S is no vertical curvature alignment along Dunvale. Both the northbound and southbound approaches to the intersection have straight horizontal alignment. The posted speed limit on Dunvale within the study area is 30 miles per hour. The land use along Dunvale south of Westheimer is primarily professional offices and multi-family residential. North of Westheimer is commercial retail development. At the time of the field investigation, Westheimer had recently been overlaid with asphalt pavement. The asphalt pavement in the center of Westheimer had been milled, but the asphalt had yet to be applied in this area, leaving a slight drop-off in the middle of the Dunvale at Westheimer intersection. During the field visit, it was observed that traffic slowed considerably while crossing the intersection on Dunvale which caused poor traffic operations and potential rear end collisions. The pavement condition on Westheimer was observed to be in excellent condition. The pavement along Dunvale appeared to be in good condition. The intersection of Westheimer and Dunvale is controlled by a semi-actuated traffic signal which operates within a coordinated traffic signal system. The traffic signal is a span-wire design application with strain pole installation. The traffic control provides for protected left turn phasing and separate left turn bays for eastbound and westbound directions. The signal operates with split phasing for the northbound and southbound directions. This phasing pattern provides protected movements for each direction separately, thus allowing their respective left turns to operate along with the corresponding through movement. Split phasing is necessary due to the lack of left turn bays on these approaches. The details of the intersection geometry, traffic and pedestrian signals, pavement markings, and signs are shown on the intersection layout (refer to Appendix A - Exhibit A3). The signal heads were observed to be in good condition. Pavement markings on Westheimer consist of reflective striping that was recently installed on the new asphalt 3-4 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S overlay and thus, were in excellent condition. The pavement markings on Dunvale consist of reflective striping and raised pavement markers. These markings and the pedestrian crosswalks and stop lines on the Dunvale and K-Mart driveway approaches were observed to be in poor condition. Minor sight distance restrictions were observed for northbound and southbound traffic. A bus stop shelter and utility poles on the southwest corner and the traffic signal cabinet and utility poles on the northeast corner restrict visibility. The sight distance is needed by motorists making a right turn on a red signal. These motorists must drive forward near the outside travel lane of Westheimer in order to see Westheimer traffic. 3-5 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S SECTION 4 SAFETY ANALYSIS This section describes the hazard reduction analysis, benefit cost analysis and results of the safety evaluation conducted at the two study intersections. 4.1 Hazard Reduction Analysis The first step in this process is to study the crash data and summarize the crashes in collision diagrams. For the study intersections, the traffic accident reports obtained from HPD for the most recent two year period were reviewed and the crashes were plotted graphically on collision diagrams. These diagrams are shown in Appendix B as Exhibits B1 through B6. The benefit cost analysis guidelines provided in TxDOT s Traffic Operations Manual Traffic Accident Information and Hazard Elimination Program Volume generally require three years of crash data (1). The DPS data obtained for the years 1998 and 1999 from H-GAC were decoded using the DPS Master Accident Decoding Manual (2). This decoded data is summarized in Appendix D as Tables D1 and D2. DPS data provides general information regarding crashes that have occurred at the study intersection, but it does not provide specific details about crash location, driver behavior, and some other pertinent factors. When accident reports are not available, the DPS data can be used almost as effectively for the analysis. The evaluation of crashes using the reports furnished by HPD was deemed most appropriate for this study given the detailed information that they contain. The next step is to review accident reports in detail, looking for crash patterns, and identify crashes that are correctable. This step required a thorough investigation of the 4-1 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S crash data. The specific types of collisions and possible contributing factors were analyzed. Each report was reviewed to determine the root cause of the crash and whether the crash could have been prevented by an improvement at the intersection. Although there were a substantial number of crashes at the study intersections, many were considered not correctable. These include crashes that were caused by driver inattention, speeding, or other non-intersection related factors. However, a portion of the crashes were attributed to intersection related factors such as driver confusion of lane assignments, slow speed for turning maneuvers due to minimal intersection curb radii, and poor signal visibility. These crashes were considered preventable by certain corrective measures. These corrective measures are outlined in this report. The next step is to identify proposed improvements to correct each preventable crash type. The Traffic Operations Manual Traffic Accident Information and Hazard Elimination Program Volume guidelines provide corrective measures, called work codes, which are grouped into the following five categories (1): Signing and Signals Roadside Obstacles and Barriers Resurfacing and Roadway Lighting Pavement Markings Roadway Work The work codes, descriptions, and definitions are provided in Appendix B Hazard Elimination Program Work Codes of the Traffic Operations Manual Traffic Accident Information and Hazard Elimination Program Volume (1). For a given preventable crash, a corrective measure (i.e., work code) was selected from the listed improvements. The associated preventable crashes were categorized by severity (i.e., Fatal and Incapacitating, Other Injury, and Property Damage Only) and the respective crashes were quantified for use in the benefit cost analyses. 4-2 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S The final step is to estimate the cost of the proposed improvements. Preliminary construction cost estimates were completed for each of the proposed improvements at the study intersections. These estimated costs were used in the benefit cost analysis. 4.2 Benefit Cost Analysis The benefit cost analysis methodology employed in this study directly follows the guidelines provided in TxDOT s Traffic Operations Manual Traffic Accident Information and Hazard Elimination Program Volume (1). The benefit cost formula, known as the Safety Improvement Index (SII), is simply the ratio of the expected cost of the reduction in crashes to the cost of constructing the proposed improvement. Section 4 Using the Safety Improvement Index of the Traffic Operations Manual Traffic Accident Information and Hazard Elimination Program Volume is provided in Appendix C for reference of the SII formula and the associated parameters (1). Adjustment factors are incorporated into the SII to allow more benefit for growth in traffic, reduction in maintenance costs, and long service lives over which construction costs can be amortized. H-GAC s projected annual traffic growth rate for the Houston metropolitan area of approximately 1.9 percent was used as the growth factor in this analysis. The percentage reduction factor for a given corrective measure (i.e., work code) is a primary parameter in the benefit cost analysis. This factor is the percentage reduction in costs or severity that can be expected as a result of the improvement. A percentage reduction factor was selected for the associated work code from Appendix B Hazard Elimination Program Work Codes of the Traffic Operations Manual Traffic Accident Information and Hazard Elimination Program Volume (1). In addition, the service life for the given improvement was selected from Appendix C Hazard Elimination Program Service Lives of the Traffic Operations Manual Traffic Accident Information and Hazard Elimination Program Volume (1). 4-3 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S The estimated cost of crashes is critical to the benefit cost analysis. The average cost of each type of crash is determined by TxDOT each year for use in the analysis. The cost estimates are based on National Safety Council (NSC) cost figures. The NSC provides annual comprehensive costs, which include economic costs (i.e., wage and productivity loses, medical expenses, administrative expenses, and motor vehicle damage) and a measure of the lost quality of life associated with deaths and injuries. The NSC categorizes the comprehensive costs into five levels of crash severity: fatality, incapacitating injury, non-incapacitating injury, possible injury, and no injury (3). It appears that TxDOT groups the cost estimates for fatality and incapacitating injury together and the cost estimates of non-incapacitating and possible injury together and determines average costs for three categories. This study used the cost data furnished by TxDOT Traffic Operation Division for 2002 as follows: Costs of fatal and/or incapacitating injury crashes: $252,000 per crash Costs of non-incapacitating and/or possible injury crashes: $17,600 per crash Costs of property-damage-only (PDO) crashes: $1,969 per crash SII results greater than or equal to 1.0 are considered cost effective. According to the guidelines, the SII was designed to compare projects and establish project priorities. The guidelines caution against using the SII results as a measure for independent projects. Having all the variable information analyzed and compiled, the SII was calculated for each of the proposed improvements and the results are presented in the following section. 4-4 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S 4.3 Analyses Results For the two study intersections, the results of the analyses are given below. 4.3.1 Westheimer at Chimney Rock The crashes that have occurred at the Westheimer and Chimney Rock intersection for the most recent two year period are graphically represented in collision diagrams shown in Appendix B as Exhibits B1 through B3. Fifty-eight (58) crashes were reported at the intersection. Of these, there were 41 rear-end, 9 side-swipe, 4 right-angle, 2 left turn, and 2 pedestrian-involved crashes. The data indicates that the dominant crash type at this intersection was rear-end crashes, i.e., a vehicle stopped for traffic is struck from behind by a following vehicle. Another crash type evident at the intersection was side-swipe crashes, i.e., a vehicle in one lane is struck in the side by another vehicle traveling in the same direction. In addition, right-angle crashes, where a vehicle in the intersection is struck broadside by another vehicle, and left turn crashes, where a vehicle is hit while turning across traffic, occurred at the intersection. As explained previously, there were a number of crashes that were not considered correctable due to contributing factors non-related to the intersection design. For example, many of the rear-end crashes were caused by driver inattention, speeding, and heavy traffic congestion. The detailed review of accident reports identified 16 traffic crashes that would be preventable by corrective measures. The number and severity of preventable crashes; the suggested improvements with associated TxDOT work codes, percentage reduction factors, service lives, and preliminary cost estimates; and the benefit cost ratios (SII) are summarized in Table 4-1 for Westheimer at Chimney Rock. The corrective measures (i.e., work codes) selected from Appendix B Hazard Elimination Program Work Codes of the Traffic Operations 4-5 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Manual Traffic Accident Information and Hazard Elimination Program Volume to mitigate preventable crashes at this intersection were identified as improve traffic signals, install pavement markings, lengthen left turn lane, and increase curb radii. Of the total of 16 crashes that were considered preventable, 9 were determined to be susceptible to correction by an improved traffic signal or signal operation. These 9 crashes, listed under TxDOT work code 108, were primarily right angle or rear end crashes (6 and 2 respectively). The crash patterns indicate that most of them occurred during the dawn or dusk hours when visibility of signal heads along Westheimer are affected due to the sun s glare. Signal improvements that include LED signals and backplates can alleviate this problem. Another factor observed based on existing signal timing is the use of shorter yellow clearance times for all signal phases at this location that is below the current standard City of Houston guidelines. Revising these values could also possibly reduce the incidence of crashes. The suggested upgrades to the existing signal include 12 LED signal heads, overhead lane use signs, backplates, and pedestrian heads and push buttons. These improvements would provide better signal visibility and enhance the driver s ability to see signal indications, especially along Westheimer, which is an east-west roadway having substantial sun glare in the morning and afternoon. The upgrade of the existing signal would cost approximately $60,000 and have an annual maintenance savings of an estimated $2,000 in electrical and operation costs. The benefit cost ratio for these improvements is 6.39. Of the 3 crashes that occurred, listed under TxDOT work code 401, two of them were due to dual left turns from Westheimer. Hence provision of clearly defined cat-tracks to demarcate the paths for these turning vehicles would reduce the probability for these type of crashes. The only other crash listed under this code could have been avoided with better pavement markings at this intersection. Re-striping the intersection to provide reflective pavement markings and markers would be expected to mitigate the side-swipe crashes that occur because the driver is unsure of the proper lane use at the intersection 4-7 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S and therefore, makes abrupt lane changes. Striping improvements at this intersection would cost approximately $4,000. Although the improvement has a low construction cost, the fact that there were only a few preventable crashes and the severity of these crashes was minor (i.e., property damage only) resulted in a low benefit cost ratio of 0.53. One crash listed under work code 520, was due to inadequate storage length for the northbound left turn lane. An improvement to lengthen the northbound left turn lane at the intersection may reduce rear-end crashes by providing additional storage space for left turning traffic and mitigate the potential for the traffic to spill out into the through traffic lanes. The construction cost for this improvement is estimated to be approximately $20,000. The resulting benefit cost ratio is 0.83. Of the 3 crashes that occurred, listed under TxDOT work code 524, two were due to vehicles being rear ended while making a right turn from eastbound Westheimer to Chimney Rock and the other occurred near the northeast corner due to a right turning vehicles not staying in the right lane while making the maneuver. The corrective measure would be to increase the curb radii at the northeast and southwest corners of the intersection. Increasing the curb radius at these corners would facilitate easier right turn maneuvers, thereby reducing the probability for similar crashes. The cost to construct the longer radii is an estimated $8,000. The benefit cost analysis resulted in a benefit cost ratio of 5.67. In summary, an upgrade to the traffic signal provides the best benefit cost ratio among the possible improvements. Increasing the curb radii also provides a good benefit cost ratio. These measures should be considered to mitigate traffic crashes at the Westheimer and Chimney Rock intersection. 4-8 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S 4.3.2 Westheimer at Dunvale The crash experience at the Westheimer and Dunvale intersection for the most recent two year period is shown on collision diagrams in Exhibits B4 through B6 of Appendix B. A total of 73 crashes were reported at the intersection. Of these, there were 60 rear-end, 7 side-swipe, 4 right-angle, 1 left turn, and 1 pedestrian-involved crashes. The major type of crash at this intersection was clearly rear-end crashes, i.e., a vehicle stopped for traffic is struck from behind by a following vehicle. Side-swipe crashes, i.e., when a vehicle in one lane is struck in the side by another vehicle traveling in the same direction, was the next dominant type of crash. In addition, several right-angle crashes, where a vehicle in the intersection is struck broadside by another vehicle, and left turn crashes, where a vehicle is hit while turning across traffic, occurred at the intersection. Many of the rear-end crashes were caused by other contributing factors not associated with the intersection design. It appears that driver inattention and traffic congestion caused the majority of these crashes. The accident report analysis found 30 traffic crashes that were determined to be preventable by corrective measures. The number and severity of preventable crashes; the suggested improvements with associated TxDOT work codes, percentage reduction factors, service lives, and preliminary cost estimates; and the benefit cost ratios (SII) are summarized in Table 4-2 for Westheimer at Dunvale. The corrective measures (i.e., work codes) selected from Appendix B Hazard Elimination Program Work Codes of the Traffic Operations Manual Traffic Accident Information and Hazard Elimination Program Volume to mitigate preventable crashes at the Westheimer and Dunvale intersection were identified as improve traffic signals, install pavement markings, add left turn lanes, and increase curb radius. 4-9 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Of the total of 30 crashes that were considered preventable at this location, 15 were determined to be susceptible to correction by an improved traffic signal or signal operation. These 15 crashes, listed under TxDOT work code 108, were primarily rear end or right angle crashes (10 and 4 respectively). The crash patterns indicate that most of them occurred during the dawn or dusk hours when visibility of signal heads along Westheimer are affected due to the sun s glare. Signal improvements that include LED signals and backplates can alleviate this problem. Another factor observed based on existing signal timing is the use of shorter yellow clearance times for traffic on Westheimer that is below the current standard City of Houston guidelines. Revising these values could also possibly reduce the incidence of crashes, especially right angle crashes. An upgrade to the existing signal should include providing 12 LED signal heads, overhead lane use signs, backplates, and pedestrian heads and push buttons. The upgrade of this existing signal would cost approximately $50,000 with annual maintenance savings of an estimated $2,000 in electrical and operations costs. The preventable crashes included injury crashes as well as property damage only crashes. These factors resulted in a benefit cost ratio of 8.77. Of the 8 preventable crashes that occurred, listed under TxDOT work code 401, most of them occurred due to inadequate striping on Dunvale, with 6 of them being side swipes. Lane use pavement markings are completely lacking on the southbound approach. The installation of reflective pavement markings and markers to show appropriate lane use would mitigate side-swipe crashes that occur when the driver is unsure of the proper lane use at the intersection and makes sudden lane changes. One of the preventable crashes involved a pedestrian, and re-striping the crosswalks along with improved pedestrian signals could reduce the chances for a similar crash. Re-striping the pavement markings at this intersection would cost approximately $4,000. Since a large number of crashes identified could be mitigated with this corrective measure, the benefits far outweigh the costs; hence, a benefit cost ratio of 25.32. 4-11 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S About 6 preventable crashes, listed under TxDOT work code 519, occurred due to motorist confusion based on existing lane assignment along Dunvale. The predominant type of crashes observed were side swipes due to motorists making abrupt lane changes when they approach the intersection. The reassignment of lane use for the northbound and southbound approaches to provide left turn only lanes with shared thru plus right lanes is one possible corrective measure to mitigate crashes. This measure can be achieved with pavement striping, advance lane use signing, and signal timing modifications. It has a relatively low construction cost of $4,500. The benefit cost ratio is 23.16. The one preventable crash listed under TxDOT work code 524, was due to a vehicle being rear ended while making a right turn from eastbound Westheimer on to Dunvale. Increasing the curb radius at the southwest corner of the Westheimer and Dunvale intersection would be a corrective measure. This improvement would reduce the incidence of vehicles slowing down on Westheimer while turning onto Dunvale. The cost to construct the larger radii is an estimated $4,000. The benefit cost analysis resulted in a benefit cost ratio of 1.03. In summary, the corrective measure that would provide the greatest safety benefit at the Westheimer and Dunvale intersection is to install pavement markings. This improvement has the best benefit cost ratio among the possible improvements. However, all of the improvements had benefit cost ratios greater than one and should be considered. 4-12 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S SECTION 5 SUMMARY This report summarizes traffic crash data, hazard reduction analysis and benefit cost analysis for two study intersections, Westheimer at Chimney Rock and Westheimer at Dunvale. The information presented in this report will assist H-GAC in the development of a Transportation Safety and Hazard Elimination Program for the Houston-Galveston region to improve traffic safety on roadways throughout the area. The objective of this study was to demonstrate the methodology to investigate high risk crash locations for safety improvements. The two study intersections were evaluated based on crash experience with specific improvements identified. Future safety investigations can utilize the methodology established in this study. This will provide H-GAC and their participating agencies with a consistent and reliable approach to improve public safety. 5-1 Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S REFERENCES 1. Texas Department of Transportation. Traffic Operations Manual Traffic Accident Information and Hazard Elimination Program Volume. Austin, Texas, 2002 2. Texas Department of Public Safety. DPS Master Accident Decoding Manual. Austin, Texas. 3. National Safety Council. Estimating the Costs of Unintentional Injuries, 2001. Statistics Department. August 2002. Accessed via www.nsc.org. Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S APPENDIX A EXHIBITS Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S APPENDIX B COLLISION DIAGRAMS Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S APPENDIX C TxDOT HAZARD ELIMINATION PROGRAM (Section 4 Using the Safety Improvement Index) Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S APPENDIX D DPS ACCIDENT DATA Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S APPENDIX E SIGNAL TIMING PLANS Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S APPENDIX F PHOTOGRAPHS Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Westheimer at Chimney Rock Photograph 1 Chimney Rock looking north, south of Westheimer (1) Photograph 2 Chimney Rock looking north, south of Westheimer (2) Photograph 3 Existing signs and signal heads for northbound Chimney Rock at Westheimer Photograph 4 Looking west from southeast corner of Westheimer at Chimney Rock (1) Photograph 5 Looking west from southeast corner of Westheimer at Chimney Rock (2) Photograph 6 Westheimer looking east, west of Chimney Rock (1) Photograph 7 Westheimer looking east, west of Chimney Rock (2) Photograph 8 Existing signs and signal heads for eastbound Westheimer at Chimney Rock Photograph 9 Looking north from southwest corner of Westheimer at Chimney Rock Photograph 10 Chimney Rock looking south, north of Westheimer Photograph 11 Existing signs and signal heads for southbound Chimney Rock at Westheimer Photograph 12 Looking east from northwest corner of Westheimer at Chimney Rock Photograph 13 Westheimer looking west, east of Chimney Rock (1) Photograph 14 Westheimer looking west, east of Chimney Rock (2) Photograph 15 Existing signs and signal heads for westbound Westheimer at Chimney Rock Photograph 16 Looking south from northeast corner of Westheimer at Chimney Rock Westheimer at Dunvale Photograph 17 Dunvale looking north, south of Westheimer Photograph 18 Existing signs and signal heads for northbound Dunvale at Westheimer Photograph 19 Looking west from southeast corner of Westheimer at Dunvale (1) Photograph 20 Looking west from southeast corner of Westheimer at Dunvale (2) Photograph 21 Westheimer looking east, west of Dunvale Photograph 22 Existing signs and signal heads for eastbound Westheimer at Dunvale Photograph 23 Looking north from southwest corner of Westheimer at Dunvale Photograph 24 Dunvale looking south, north of Westheimer Photograph 25 Existing signs and signal heads for southbound Dunvale at Westheimer Photograph 26 Looking east from northwest corner of Westheimer at Dunvale (1) Photograph 27 Looking east from northwest corner of Westheimer at Dunvale (2) Photograph 28 Westheimer looking west, east of Dunvale Photograph 29 Existing signs and signal heads for westbound Westheimer at Dunvale Photograph 30 Looking south from northeast corner of Westheimer at Dunvale Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 1. Chimney Rock looking north, south of Westheimer (1) Photograph Date: 09/17/2002 Photograph 2. Chimney Rock looking north, south of Westheimer (2) Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 3. Existing signs and signal heads for northbound Chimney Rock at Westheimer Photograph Date: 09/17/2002 Photograph 4. Looking west from southeast corner of Westheimer at Chimney Rock (1) Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 5. Looking west from southeast corner of Westheimer at Chimney Rock (2) Photograph Date: 09/17/2002 Photograph 6. Westheimer looking east, west of Chimney Rock (1) Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 7. Westheimer looking east, west of Chimney Rock (2) Photograph Date: 09/17/2002 Photograph 8. Existing signs and signal heads for eastbound Westheimer at Chimney Rock Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 9. Looking north from southwest corner of Westheimer at Chimney Rock Photograph Date: 09/17/2002 Photograph 10. Chimney Rock looking south, north of Westheimer Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 11. Existing signs and signal heads for southbound Chimney Rock at Westheimer Photograph Date: 09/17/2002 Photograph 12. Looking east from northwest corner of Westheimer at Chimney Rock Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 13. Westheimer looking west, east of Chimney Rock (1) Photograph Date: 09/17/2002 Photograph 14. Westheimer looking west, east of Chimney Rock (2) Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 15. Existing signs and signal heads for westbound Westheimer at Chimney Rock Photograph Date: 09/17/2002 Photograph 16. Looking south from northeast corner of Westheimer at Chimney Rock Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 17. Dunvale looking north, south of Westheimer Photograph Date: 09/17/2002 Photograph 18. Existing signs and signal heads for northbound Dunvale at Westheimer Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 19. Looking west from southeast corner of Westheimer at Dunvale (1) Photograph Date: 09/17/2002 Photograph 20. Looking west from southeast corner of Westheimer at Dunvale (2) Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 21. Westheimer looking east, west of Dunvale Photograph Date: 09/17/2002 Photograph 22. Existing signs and signal heads for eastbound Westheimer at Dunvale Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 23. Looking north from southwest corner of Westheimer at Dunvale Photograph Date: 09/17/2002 Photograph 24. Dunvale looking south, north of Westheimer Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 25. Existing signs and signal heads for southbound Dunvale at Westheimer Photograph Date: 09/17/2002 Photograph 26. Looking east from northwest corner of Westheimer at Dunvale (1) Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 27. Looking east from northwest corner of Westheimer at Dunvale (2) Photograph Date: 09/17/2002 Photograph 28. Westheimer looking west, east of Dunvale Traffic Accident Analysis

KLOTZ ASSOCIATES, INC. C O N S U L T I N G E N G I N E E R S Photograph Date: 09/17/2002 Photograph 29. Existing signs and signal heads for westbound Westheimer at Dunvale Photograph Date: 09/17/2002 Photograph 30. Looking south from northeast corner of Westheimer at Dunvale Traffic Accident Analysis