Roadway Conditions as Contributing Factors in Florida Traffic Crashes

Transcription

1 Roadway Conditions as Contributing Factors in Florida Traffic Crashes Michael R. Baltes and Xuehao Chu Center for Urban Transportation Research University of South Florida 4202 East Fowler Avenue, CUT 100 Tampa, FL ABSTRACT One of the primary goals of the Florida Department of Transportation (Florida DOT) is to reduce the number and severity of crashes that occur on the State Highway System (SHS) each year, or that portion of Florida s roads under the Florida DOT s control. The Florida DOT s main goal is to keep the percentage of crashes on the SHS where roadway conditions are contributing factors below one percent through the year As defined by the Florida Department of Highway Safety and Motor Vehicles, roadway conditions include such factors as standing water; loose surface materials; holes, ruts, and unsafe paved edges; and worn or polished roadway surfaces, for example. The findings from the research indicated that the use of roadway conditions as a performance indicator is not warranted. The estimate of the number of 1998 crashes on the SHS where a roadway condition was shown to be a contributory factor to its occurrence was very low. Out of the final sample crashes, only a total of 204 crashes indicated a roadway condition that could be potentially correctable by a Florida DOT action. The net result was a total number of crashes that was so minimal that the determination of a significant problem cannot be made where corrective action by the Florida DOT could minimize or reduce the number of future crashes. Projecting the sample to all of the 1998 traffic crashes that occurred on the SHS in Florida, only 0.7 percent of could have potentially been influenced by Florida DOT corrective actions. Key words: crash data crash report roadway conditions sample of crashes traffic control Proceedings of the 2003 Mid-Continent Transportation Research Symposium, Ames, Iowa, August by Iowa State University. The contents of this paper reflect the views of the author(s), who are responsible for the facts and accuracy of the information presented herein.

2 INTRODUCTION One of the primary goals of the Florida Department of Transportation (Florida DOT) in its Florida Transportation Plan is to reduce the number and severity of crashes that occur on the State Highway System (SHS), or that portion of Florida s roads under Florida DOT control. As stated in its 1999 Annual Report, the Florida DOT s main goal is to keep the percentage of crashes on the SHS where roadway conditions are contributing factors below one percent through the year The primary purpose of conducting this special research project for the Florida DOT was to determine whether the percent of 1998 Florida traffic crashes noting a roadway contributing condition could serve as a reliable Florida DOT performance indicator for measuring safety on the SHS. As defined by the Department of Highway Safety and Motor Vehicles (DHSMV), roadway conditions include such factors as standing water; loose surface materials; holes, ruts, and unsafe paved edges; and worn or polished roadway surfaces, for example. It should be noted that the investigation of conditions or defects caused by the design of roadways that are part of the SHS was not included as an element of the research project. The Florida DOT requested the assistance of the Center for Urban Transportation Research (CUTR) at the University of South Florida, Tampa, to complete this project using 1998 Florida traffic crash data, the most recent available at the time. This paper presents the findings and recommendations from the fourth study. METHODOLOGY Data collection involved several simple steps. First, Florida traffic crash data for calendar year 1998 were requested from the DHSMV from its Statewide Accident Management Information System (STAMIS) electronic crash database. In the previous three studies, electronic traffic crash data were obtained from the SSO and not the DHSMV (with a few minor differences, the crash data are identical) (1, 2, 3). Second, using specific parameters, a sample of applicable crashes (those that occurred on the SHS with a roadway condition code other than Code-01 or no defects) was developed using the random sample generator in SPSS The final step in the collection of crash data involved obtaining hard copies of the crash reports from the SSO. By selecting certain information contained in specific crash variables, the research team was able to create a database that contained only those crashes that occurred on the SHS with a noted roadway condition numerical code value other than 01 (no defects). The variable road system identifier in the DHSMV crash database contained the information about roadway types. This particular variable lists seven roadway types (numerically coded as 01 through 07) and Code-77, which represents all other roadway identifiers not listed among the first seven such as forest and fire roads. For this variable, SHS roadways were numerically coded as follows: 01 (interstate), 02 (US), 03 (state), and 06 (tolls/turnpikes). Again, the SHS is comprised of those roadways that are included in the Florida DOT s Roadway Characteristics Inventory and are under its direct purview. This procedure resulted in a database that included a total of 3,077 crashes that occurred on the SHS with a noted roadway condition code other than 01 (no defects). Using the crash report number as the key, information from each of the four DHSMV sub-files (Events, Driver, DOT Site, and Vehicle) were merged into a final crash database that contained the following data elements (for reference, the corresponding STAMIS sub-file is listed next to each data element): County (Events File) City (Events File) Crash report number (Events File) Baltes and Chu 2

3 Date (Events File) Injury severity (Events File) Total property damage (Events File) Number of lanes (Events File) First harmful event (Events File) Road system identifier (Events File) Lighting condition (Events File) Road surface condition (Events File) Weather (Events File) Road surface type (Events File) First contributing cause road (Events File) First traffic control (Events File) DOT milepost (DOT Site Location File) DOT average daily traffic (DOT Site Location File) DOT highway location (DOT Site Location File) State road number (DOT Site Location File) Driver injury severity (Driver File) Driver age (Driver File) Department District (derived based on the variable County from the Events File) The next step was to develop a sample of traffic crashes from the database that contained the 3,077 crashes that occurred on the SHS with a noted roadway condition code other than 01 (no defects). The initial sample of crashes were ultimately developed by selecting approximately 25 percent of the individual crash records within each Department district using the simple random sample generator available in SPSS This approach ensured that each Department district would be represented proportionally in the final sample of traffic crashes. This process resulted in an initial study sample of 900 crashes out of the possible 3,077. For comparison, the size of the final samples for the three previous studies varied from 50 percent (1995), 25 percent (1996), and 15 percent (1997) of the crashes that met the criteria for sampling. Based on the results from the assignment of detailed causality codes, the crash reports that were actually coded as 01 (no defects) but transcribed incorrectly by DHSMV data entry staff, plus others that were either missing the crash narrative and/or diagram or had other incomplete information that prohibited an accurate application of one of the detailed causality codes were eliminated from the initial sample (n = 900). After these eliminations, the remaining number of crash reports in the final sample was 728. Unfortunately, the computerized crash data obtained from the DHSMV does not contain the crash report narrative and diagram. The crash narrative and diagram were critical to properly identifying the quality and accuracy of the crash data as well as any cause-and-effect relationships that may have existed in the data. Therefore, actual crash reports archived at the SSO needed to be obtained and reviewed in detail by the CUTR research team. Once copies of the crash records were in hand, their analysis took several steps. The first step involved the classification of roadway conditions noted on each crash report. This required a researcher to study each crash report intensively by carefully reading the narrative and examining the diagram to identify the role, if any, of the listed road-related contributing factors. If cause was determined, a code was applied to each crash report and entered into the crash database that contained the initial sample of crashes. Since the most critical information was contained in the narrative and diagram portion of the crash reports, a set of detailed codes was used to categorize roadway conditions. Initially developed in Baltes and Chu 3

4 conjunction with Florida DOT staff, these detailed codes were created to show more specific information about the contribution that roadway conditions may have played in crashes. The first step when analyzing the crash report narratives and diagrams was to make an assessment of whether each crash report was consistent with the roadway condition code originally assigned by the reporting law enforcement officer. The next step was to determine whether the reporting law enforcement officer had described the effect of the indicated roadway condition in the crash report narrative and/or diagram. This was the most critical and time consuming step in the process of analyzing the initial sample of crash reports. Based on the methodology devised for use in the three prior studies, the initial sample of crash reports was first classified according to whether any mention or reference to the roadway condition was made in the crash report narrative and/or diagram by the reporting law enforcement officer. It was envisioned that the roadway conditions could be clearly identified and their contribution explained in the narrative and/or in the diagram of the crash reports. If no reference was found to the indicated roadway condition in either the crash report narratives or diagrams, the decision was that the listed roadway condition played no contributing role in the occurrence of the crashes but instead was merely present at the time of the crashes. For example, if a law enforcement officer indicated loose surface materials (roadway condition Code-04) but failed to mention anything specific about the nature and involvement of the loose surface materials in the crash report narrative and/or diagram, it was concluded that the reporting law enforcement officer did not consider the loose surface materials to have been a contributing factor in the occurrence of the crash (i.e., treated as a no-defect crash). Based on the detailed causality codes, these particular reports were assigned one of the following numerical codes: 299, 399, 499, 599, 699, 799, or 899. These particular detailed causality codes indicate that the reporting officers on the crash reports did not note the roadway condition in either the narratives and/or diagrams. The remainder of the crash reports were reviewed and assigned a corresponding detailed causality code. In a few instances, crash reports may have also received a second detailed causality code; particular in those instances where it was determined that an additional roadway condition may have also played a role in the occurrence of the crashes. The last step was to identify those crashes that contained a potentially correctable roadway condition that the Florida DOT could possibly use when devising strategies to eliminate or reduce future hazardous roadway conditions. The crash reports that were coded as potentially correctable using the set of detailed codes were determined to be the best source for developing a roadway condition performance indicator. Again, this determination was based on the need for the performance indicator to determine the number of crashes that may actually be avoided or reduced through some type of corrective action by the Florida DOT via its roadway maintenance program. This means that the identified roadway conditions that are not directly correctable by an action of the Florida DOT such an environmental obstruction or a severe weather condition were eliminated from consideration during assessment. After a detailed cause code was applied to each crash report (assuming cause was determined), the code was entered into the crash database for analysis to identify any possible trends and correlations that may have existed within the crashes. RESULTS As mentioned, one of the primary goals of the project being reported on in this paper was to determine whether the percent of crashes noting a roadway condition could serve as a reliable agency performance indicator for highway safety. As in previous studies, the decision was once again to be based on whether one or more cause-and-effect relationships could be established within the traffic crash data. The analysis of 1998 Florida traffic crash data shows that no one such relationship could be established. Thus, there was no strategic issue present with regard to roadway conditions as contributing factors in Florida traffic crashes. In addition, for numerous reasons such as the low quality of the crash data mainly due to Baltes and Chu 4

5 inaccurate application of the actual roadway condition by officers, the use of this data element in its current form is unsuitable as a measure for the Florida DOT to use when gauging its safety performance with regard to the SHS. Several findings were uncovered related to the accuracy and validity of the 1998 Florida traffic crash data. Detailed investigation of the final sample of crashes shows a very high degree of coding agreement between the data entries in the electronic DHSMV crash database (which was assumed to be correct by users) for the roadway conditions data element and the entries actually noted by law enforcement officers on the written crash reports acquired from the SSO. Detailed inspection indicated that only 1.5 percent of the crash reports in the final sample obtained from the SSO were found to have been coded incorrectly by DHSMV data entry staff when transcribing crash information into electronic format. In eight of the instances the hard copy crash reports were actually coded as 01 (no defects) by law enforcement officers but were mistakenly transcribed by DHSMV data entry staff as one of the other possible eight contributing cause codes (Codes 02-77). For example, in two instances, crash reports that were coded as 01 (no defects) by officers were listed in the DHSMV electronic database as Code-02 (obstruction with/without warning). The detailed inspection of the hard copy crash reports also indicated that Code-77 (all other, explain) represents a special case with respect to the quality and accuracy of the transcribed crash data in the DHSMV electronic database. In 5.2 percent of the final sample it was revealed that DHSMV data entry staff indicated Code-77 (all other, explain) as the roadway condition when an officer did not indicate one of the possible roadway contributing cause codes (i.e., he/she either unintentionally or intentionally left the box entirely blank, wrote unknown, or crossed through the check box) on the crash report. When transcribing crash data, it appears that DHSMV data entry staff did not attempt to make a determination of the roadway contributing cause in these cases using the crash report narratives and/or diagrams and, instead, indiscriminately applied Code-77 (all other, explain). Based on the information provided in the crash report narratives and diagrams in each of these instances it was determined by the research team that Code-01 (no defects) should have originally been applied to these particular crash reports by law enforcement officers instead of leaving the box blank. It should be noted, however, that the research team believes these instances to actually be the result of DHSMV data entry procedure rather than an issue of data quality or accuracy. The degree of coding agreement by roadway condition factor is shown in Table 1. The findings also indicated that the use of roadway conditions as a performance indicator was not warranted. The estimate of the number of 1998 crashes on the SHS where a roadway condition was shown to be a contributory factor to its occurrence was very low. Out of the final sample crashes, only a total of 204 indicated a roadway condition that could be potentially correctable by a Florida DOT action, as shown in Table 2. The net result was a total number of crashes that was so minimal that the determination of a significant problem cannot be made where corrective action by the Florida DOT could minimize or reduce the number of future crashes. Projecting the sample to all of the 1998 traffic crashes that occurred on the SHS in Florida, only 0.7 percent of could have potentially been influenced by Florida DOT corrective actions. This finding meets the Florida DOT s goal of less than one percent of the crashes on the SHS in which a roadway condition was a contributing factor. The analysis of the final sample of 1998 traffic crash reports showed that the roadway codes utilized by law enforcement was not well documented in the narrative and/or diagram portion of the crash reports contained in the final sample. This results in an overestimation of road-related contributing condition crashes and/or the absence of useful data with which t address any actual contributions of the roadway conditions in crashes. Baltes and Chu 5

6 TABLE 1. Coding Inconsistencies by Contributing Roadway Condition Factor (1998) Roadway Contributing Condition Code Description Number in Sample 1 Percent of Sample Number of Inconsistencies Percent Inconsistency by Factor 02 Obstruction with or without warning % 4 6.2% 03 Road under repair or construction % 1 0.4% 04 Loose surface materials % % 05 Shoulders soft, low, or high % 1 5.0% 06 Holes, ruts, or unsafe paved edge % 0 0.0% 07 Standing water % 1 0.7% 08 Worn or polished road surface % 0 0.0% 77 All other, explain % % Total % % 1 The crash reports that were actually coded as 01 (no defects), plus the other crash reports that were missing the narrative and/or diagram or had other incomplete information that prohibited an accurate determination of the detailed roadway contributing cause were eliminated from the initial sample of 900 crashes. The final sample after these eliminations had 728 crashes. Many law enforcement officers are simply entering one of the possible roadway conditions only when one of the conditions or factors was present instead of when it was observed to have directly contributed to the occurrence of the crash. Based on the review of the crash reports in the final sample, in many of these instances the reporting law enforcement officers should have indicated Code-01 or no roadway conditions/defects. It also appears that officers made no attempt whatsoever to determine what, if any, roadway condition(s) might have lead to the occurrence of the crashes contained in the final sample. For example, the application of the detailed causality codes revealed that most of the crashes that occurred in a construction zone (Code-03) were coded as such without any thought or regard to whether there was something specific about the construction zone that contributed to the occurrence of the crash such as a ladder suddenly falling off of a construction vehicle and causing an unexpected roadway obstruction. Detailed investigation of the final sample of crash reports shows a very high degree of coding agreement between the data entries in the electronic DHSMV crash database (which was assumed to be correct by users of the crash data) for the variable first contributing cause-road and the entries actually noted by law enforcement officers on the written crash reports. DHSMV data entry staff when transcribing crash information into electronic format coded only 1.5 percent of the crash reports in the final sample incorrectly. In 5.2 percent of the final sample, it was revealed that DHSMV data entry staff indicated Code-77 (all other, explain) as the roadway condition when an officer did not indicate one of the possible roadway conditions (i.e., he/she either unintentionally or intentionally left the box entirely blank, wrote unknown, or crossed through the check box) on the crash report. Code-77 implies that a roadway condition was present that potentially contributed to the occurrence of the crash. The dilemma created by a DHSMV data entry operator coding a blank response as Code-77 is the inability to determine if a roadway condition was actually present or if the officer really left the roadway condition code box blank. Baltes and Chu 6

7 TABLE 2. Crash Reports Identifying Road Conditions Potentially Correctable by the Florida DOT by District (1998) Code Detailed Causality Code Number of Potentially Correctable Crashes by District Total Category 10 (Miscoded Reports) 120 Blank/Unknown, Most Like Category 20 (Obstruction with/without Warning) 22 Barricades Without Warning Stopped Vehicle Due to Construction 1 1 Category 30 (Road Under Repair/Construction) 31 Construction Worker Struck Struck Construction Vehicle/Barricades Construction Related Confusion/Unfamiliarity Road Surface Condition Due to Construction Impacted by Construction Related Vehicle Traffic Control Restriction Due to Construction Flagman Present Improper Traffic Control in Construction Area Obstruction Related to Construction Category 50 (Shoulder Soft/Low/High) 51 Shoulder Soft Shoulder Low Shoulder High 1 1 Category 60 (Holes/Ruts/Unsafe Paved Edges) 61 Holes in Pavement Ruts in Pavement Unsafe Paved Edge Present 2 2 Category 70 (Standing Water) 71 Flooding Due to Poor Drainage Excessive Water on Road/Standing Water, Not Defined Isolated Water on Road Hydroplaning Occurrence, Indicating Standing Water Category 80 (Worn/Polished Road Surface) 81 Fault in Road, Polished Metal Bridge Grating 2 2 Category 90 (All Other) 92 Most Like Most Like Most Like Most Like Traffic Control Malfunction Total Baltes and Chu 7

8 As noted above, officers often elect not to enter one of the nine possible roadway condition codes but to either leave blank, write unknown, or cross through the check box on the crash report for this data element even though the crash report completion procedure requires that a code entry be made in all instances. In addition, if officers feel that one of the specific roadway condition codes (01-08) does not sufficiently provide an accurate description of the circumstances that lead to the crashes, they have the option of selecting Code-77 (all other, explain), which requires further explanation of the circumstances surrounding the crashes in the narrative and diagram portion of the reports. The guidelines contained in the Instructions for Completing the Florida Uniform Traffic Crash Report Forms does not instruct law enforcement officers to explain the codes they chose in the narrative or diagram of crash reports other than Code-77 (all other, explain). Officers are simply required to describe what happened in the crash and to make the narrative and diagram as consistent as possible. As noted in prior studies on this issue, the resulting inconsistency of reporting produces an overstatement of the number of crashes on the SHS that involve a roadway condition. The various cause-and-effect analyses revealed by the crash reports does not appear to show any significant problems either by District or Department maintenance facility (County). While Florida DOT actions can be taken, this finding results in the conclusion that there was no specific strategic action that can be taken by the Florida DOT to reduce the observed number of roadway condition crashes on the SHS. While the sample included a small number of crashes that occurred on the Florida Turnpike (District Eight), construction-related and standing water accounted for the bulk of these types of crashes in the final sample. It was recommended that the Florida Turnpike staff be made aware of this finding and that they should monitor and further investigate these types of crashes to reduce occurrence since these are areas where the Florida DOT could potentially make the biggest impact via its maintenance program. Based on the review of the crash reports in the final sample, standing water often appears to be the cause of inadequate drainage or water runoff on some of the roadways that comprise the SHS. In many cases this was a problem that can readily be corrected by Florida DOT action. Of the final sample of 728 crashes, 96 involved standing water as a direct result of poor drainage (detailed cause codes 71, 73, 75, and 77). Each of the eight Districts maintenance departments need to be immediately informed of these problems as they are reported so that any necessary action can be taken to reduce the number the number of standing-water related crashes. During the course of this study, it was uncovered that SSO staff included crashes in its crash database that actually occurred on non-shs roadways or what the SSO refers to as side-road crashes. SSO staff included those crashes that occurred on a non-shs roadway within 250 feet of an intersecting SHS roadway even when the roadway conditions on the intersecting SHS roadway played no contributory role in the crash. This resulted in an overstatement of roadway condition crashes and/or the absence of useful data to be able to address any true contributions of roadway conditions in crashes on the SHS. RECOMMENDATIONS Based on the findings, it was recommended that the Florida DOT discontinue the use of the roadway conditions data element as a performance measure to improve motorist safety on the SHS. Instead, the Florida DOT should attempt to find another method as a performance indicator for measuring its safety performance regarding the SHS. Further, if Florida DOT management continues with the use of this data element as a performance measure, improvements must be made in the training of law enforcement officers statewide on the correct Baltes and Chu 8

9 application and use of this particular data element. If accurately applied by law enforcement officers when investigating the scene of crashes and subsequently completing crash reports, this data element would be the most appropriate measure for gauging the Florida DOT s performance with respect to motorist safety on the SHS. Previous studies recommended that 15-minute training sessions be prepared and implemented as part of the overall law enforcement-training program. It was recommended that these sessions be continued and the frequency that they are administered be increased with specific emphasis given to officers about the critical need for them to correctly and uniformly apply this data element. In addition, it was recommended that the procedure that officers are trained to follow be changed so that they are mandated to indicate whether or not and how roadway conditions may have contributed to crashes that occurred on the SHS. Compared to other roadway conditions, due to the high frequency of crashes caused by the presence of roadway repairs/construction and standing water, it was recommended that all crash reports with one of these noted roadway contributing factors be immediately forwarded by local law enforcement to the appropriate Department/District maintenance office or staff as deemed appropriate for further investigation and appropriate corrective action. Finally, should the Florida DOT continue with these special studies, it was recommended that a departure be made from using crash data provided by the SSO to data provided by the DHSMV. Based on the inclusion of side-road crashes, the information contained in the DHSMV database is a more accurate portrayal of crashes that actually occurred on Florida DOT maintained roads, i.e., the SHS. As a result of the inclusion of side-road crashes, the use of the SSO crash database overestimated the number of crashes that could potentially be correctable by the Florida DOT. REFERENCES 1. Florida Department of Transportation. Road-related Contributing Factors in Highway Crashes in 1995: Final Report. Office of Policy Planning, Florida Department of Transportation, Tallahassee, Florida, Florida Department of Transportation. Road-related Contributing Factors in Highway Crashes in 1996: Final Report. Office of Policy Planning, Florida Department of Transportation, Tallahassee, Florida, Florida Department of Transportation. Road-related Contributing Factors in Highway Crashes in 1997: Final Report. Office of Policy Planning, Florida Department of Transportation, Tallahassee, Florida, Baltes and Chu 9