Technical Memorandum To: The Castle Rock Town Council and Public Works Commission From: CDOT Region 1 Traffic Operations Unit RE: SH 86-Founders Pkwy/Allen Way Intersection Assessment of Alternatives INTRODUCTION Because of numerous public complaints, CDOT hass begun the design to replace the pavement on Founders Pkwy from I-25 east to Woodlands Blvd. The pavement is in extremely poor condition and requires higher than normal maintenance from CDOT staff. In conjunction with this pavement re-construction project, CDOT is proposing improvements to SH 86 (Founders Pkwy) that will address the current safety and operational concerns at the Founders and Allen Way intersection. The information provided in the following pages summarizes the result of the traffic, access and safety analyses. This information is being provided to give the Town of Castle Rock staff the opportunity to review the results and subsequent comparison of the alternatives. BACKGROUND CDOT adopted the Meadows/Founders corridor from the Town of Castle Rock in 2006 in its present configuration. The Meadows/Fo ounders corridor is within the Town of Castle Rock and is a high volume roadway that serves numerous commercial and retail interests, as well as high volumes of commuter traffic to and from I-25. Due to continued, rapid development in the area, the Founders/Allen Way intersection is currently failing to support the amount of traffic demand that occurs during the peak hour periods. EXISTING CONDITION The Founders Pkwy/Allen Way intersection is a full movement, signalized intersection located approximately 320 feet east of the signalized I-25 northbound off-ramp intersection. Because of this close intersection spacing and the high demand of traffic along Founders Pkwy, the operation and safety of these intersections is poor, and continues to degrade as time passes. This intersectionn spacing is significantly below the requirements of the State Highway Access Code, which requires a minimumm of 550 feet. Because of surrounding retail development, relocating the Allen Way intersection is not feasible. There is no formal Access Permit currently in place for Allen Way. 1
Technical Memorandum ALTERNATIVES DEVELOPMENT A Traffic Study of the Meadows/Founders corridor was completed in July 2012. Working with the results of the study, and with the Town of Castle Rock, two alternatives were developed to improve the operation and safety of the Founders/Allen Way intersection. These alternatives have been further refined and evaluated using a VISSIM traffic simulation model. Common to both alternatives is; The addition of a 3 rd eastbound through lanee from I-25 to Allen Way, Adding a 2 nd lane to the I-25 westbound to northbound on-ramp, Adding a 2 nd right turn lane on the I-25 northbound off-ramp, Adding a 2 nd southbound right turn lane on Allen Way, and Adding a westbound right turn lane on Founders Pkwy at Allen Way. The two refined alternatives are described below. Alternative 1a This alternative applies access control by restricting the northbound and southbound through and left turning traffic on Allen Way and re-directing this traffic to the east to the Front Street intersection (See Figures 1 and 7). Alternative 2a This alternative retains full movement operation at Allen Way and improves intersection operation by providing a 2 nd lane for the eastbound to northbound left turn movement and hence, more intersection capacity than the current condition (Seee Figure 2). The alternatives were evaluated based on 3 main categories; Traffic Operations Safety Access Since Alternativee 1a involves diversion of traffic at Allen Way, The Alternatives were evaluated and compared to each other based on NETWORK performance that included ALL affected intersections. 2
18500 E. Colfax Avenue (303) 365-7341 Fax (303) 365-7343 Figure 1 - Alternative 1a 3
18500 E. Colfax Avenue (303) 365-7341 Fax (303) 365-7343 Figure 2 - Alternative 2a 4
ALTERNATIVES COMPARISON A comparison of the alternatives was performed using the VISSIM traffic simulation model to better understand the pros and cons of each. The entire corridor was modeled from US 85/Meadows intersection to the Founders/Crowfoott Valley intersection. The modeling focus areaa and subsequent resultss of the VISSIM analysiss includes the following intersections and is hereby referred to as the NETWORK. Figure 3 the VISSIM Evaluation NETWORK The analysis focused on two different peak hour periods, the PM peak hour and the Weekend (WE) peak hour. These were the highest traffic use periods within the area of study. The VISSIM models incorporated the impactss of traffic diversion in the Alternative 1a assessment and subsequent increase in traffic at the Founders Pkwy/Front St and Front St/ Milestone Ave intersections, and are incorporated inn the NETWORK measures of effectiveness presented here. 5
Traffic Operations Alternative 1a This alternative showss significant improvement to traffic flow on both Founders Pkwy and the I-25 northbound off-ramp. Because of the restricted movements, signal operation can be changed at Allen Way from 8-phase to 2-phase operation. This affords a significant operational improvement by providing more green time to Founders Pkwy and for traffic coming from the I-25 off-ramp intersection. Alternative 2a This alternative showss improvement to the Allen Way intersection operation because the eastbound left turn requires shorter green times to and subsequently, gives more green time to the other intersection movements. However, the operation of the I-25 northbound off-ramp remains hampered, mostly because the Founders/Allen Way intersection retains 8-phase operation and subsequently restricts the amount of green time that can be given at the Founders Pkwy/Allen Way intersection. This is especially true during the PM peak hour. Subsequent analysis shows that significant vehicle stacking will eventually occur on the I-25 northbound off-ramp. The NETWORK delay comparison is shown in Figure 4 for both alternatives. The NETWORK vehicle Stops comparison is shown in Figure 5. Vehicle Stops and Delay within the Alternative 1a NETWORK is notably lower than the Alternative 2a NETWORK during the peak hour periods. 6
Figure 4 - Vehicle Delay Improvement over the No-Build Alternative 100% 90% 80% 70% 60% 50% 40% Alternative 1a Alternative 2a 30% 20% 10% 0% PM Peak Hour Weekend Peak Hourr Note: Table shows percent improvement when compared to the No-Action Alternative The NETWORK delay comparison shows a significant difference in performance. Alternative 1a, with access control, clearly outperforms Alternative 2a. 7
Figure 5 Vehicle Stops Comparison within the Network 140% 120% 100% 80% 60% Alternative 1a Alternative 2a 40% 20% 0% PM Peak Hour Weekend Peak Hour Note: Table shows percent improvement when compared to the No-Action Alternative At Year 2030, Alternative 1a provides 50 percent fewer NETWORK stops during the PM peak, and approximately 80 percent fewer NETWORK stops during the weekend peak hour. The NETWORK vehicle stops comparison shows a significant difference in performance. Alternative 1a, with access control, clearly outperforms Alternative 2a. 8
ACCESS CONTROL Figure 6 shows the impacts of access control and subsequent diversion of traffic. The effects of the diverted traffic on Founders Pkwy andd Allen Way are; An average of 74 percent of all the Allen Way intersection traffic is still being served even with access control. 100 percent of all traffic from Founders Pkwy to Allen Way is still being served. An average of 26 percent of the total traffic currently using the Allen Way intersection will be diverted. An average of 19 percent of the total traffic currently using the Allen Way intersection that is being divertedd is forced to travel out-of-direction. One significant reason why the NETWORK performance of alternative 1a is better than Alternative 2a is because only a relatively small percentage of the total traffic is being diverted. In order to better serve the traffic diverted to Front Street for Alternative 1a, several modifications were required at both the Founders/Front St, and at the Front St/Milestone Ave intersections. These modifications are; Change the signal phasing and lane assignments at the Founders/Front St intersection to allow 3 northbound left turn lanes. Change the signal phasing and lane assignments at the Front St/Milestone Ave intersection to allow 2 eastbound left turn lanes. Regardless of access control, The Milestone Shopping Center site layout currently offers marginal efficiency in terms of vehicle circulation. 9
DEPARTMENT OF TRANSPORTATION 18500 E. Colfax Avenue Figure 6 10
SAFETY The Founders Pkwy/Allen Way intersection is one of the highest accident locations in the corridor. A 5-year breakdown of the intersection accident types from 2008 to 2012 is provided in Figure 7 below. Figure 7 Source: CDOT Accident Database Alternative 1a access control eliminates the northbound and southbound through and left turn movements, reducing approach turn accidents by 17 percent and eliminating northbound/southbound broadside accidents. Tablee 4 shows a comparison of the number of stops between each of the alternatives. Based on the total number of intersection stops, Alternative 1a has a total average of 24 percent fewer stopss than Alternative 2a. This can be directly correlated to a 24 percent reduction in rear-end accidents. The total anticipated reduction in all accident types is approximately 35 percent with access control as provided in Alternative 1a. 11
Figure 8 highlights the safety benefits of access control by significantly reducing the number of conflict points and crossing conflict points. The safety improvement provided in Alternative 1a would only have 8 conflict points withh 2 crossing conflict points while Alternative 2a would maintain the existing 32 conflict points plus 16 crossing conflict points. Figure 8 Conflict Point Diagram 12
Vehicle Stacking (Queuing) One of the largest concerns CDOT has resulting from the operational analyses of thesee alternatives is the vehicle queuing on the I-25 northbound off ramp. This is best illustrated in Figure 9 and Figure 10. vehicle stacking queues shown for Alternative 2a are getting close to blocking traffic on I-25. Figure 9: Alternative 1a Access Control 13
Figure 10: Alternative 2a Full Movement Alternative 1a has lower levels of delay and significantly fewer vehicle stops. This is because Alternative 1a can provide significantly more green time to the Founders Pkwy eastbound movement. This analysis shows that Alternative 2a will eventually generatee excessive vehicle queuing and threatens the operation of I-25. Queuing estimates from the model shows that queuing will be in excess of 1500 feet. Further rampp lengthening is restricted by adjacent development. 14
SUMMARY The following is a summary of the conditions and findings presented in this memorandum. Description; Alternative 1a applies access control by restricting the northbound and southbound through and left turning traffic on Allen Way and re-directing this traffic to the east to the Front Street intersection (Seee Figures 1 and 6). Alternative 2a retains full movement operation and improves intersection operation by providing a 2 nd lane for the eastbound to northbound left turn movement and hence, more intersection capacity (See Figure 2). Traffic Operations; Alternative 1a NETWORK performs at a higher level of operational efficiency than Alternative 2a even with traffic diversion. Alternative 1a NETWORK has lower levels of delay and significantly fewer vehicle stops. This is because Alternative 1a can provide significantly more green time to the Founders Pkwy eastbound through movement. Alternative 2a generates excessive vehicle queuing on the I-25 northbound off-ramp and threatens the operation and safety off I-25. By the year 2030, the Alternativee 1a NETWORK clearly outperforms the Alternative 2a NETWORK. The VISSIM aggregate Performance Indices show that by the year 2030, Alternative 1a outperforms Alternativee 2a by an average of 32 percent. Access Control; The Founders Pkwy intersectionn spacing between the I-25 northbound off-ramp and Allen Way is significantly below the requirements of the State Highway Access Code, which requires a minimum of 550 feet. Becausee of the surrounding development, relocating the Allen Way intersectionn is not feasible. The change in access essentially shifts the delay experienced at the Allen Way intersection to the intersections of Founders/Front St, and Front/Milestone Ave intersections. An average of 74 percent of all the intersection traffic is still being served with access control in Alternative 1a. 100 percent of all traffic accessing Allen Way from Founders Pkwy is still being served. Diverting traffic from Allen Way to Front Street basically y relocates portions of the total NETWORK delay from Allen Way to Front St and subsequently lowers the total NETWORK delay. Safety; Due to access control at the Founders/Allenn Way intersection, Alternative 1a provides a much higher level of safety. The reduction in accidents is estimated at 35 percent. 15
Reducing the number of accidents has the additional benefit of reducing the subsequent high delays due to accidents. The reduction in the number of intersection Conflict Points at Founders/Allen Way is significantly lower for Alternativee 1a than Alternative 2a. Alternative 2a generates excessive vehicle queuing on the I-25 northbound off-ramp and threatens the safety of I-25. Criteria Network Traffic Operations Alternatives Evaluation Matrix No Action Alternative 1a (Leave as is) (Uses Access Control) Alternative 2a (Retains Full Movement) Travel Time Delay (Seconds per Vehicle) PM Peak Weekend Peak PM Peak Weekend Peak PM Peak Weekend Peak Year 20200 86 115 45 54 49 58 Year 2025 94 134 51 66 62 82 Year 20300 107 144 60 96 82 113 Number of Vehicle Stops PM Peak Weekend Peak PM Peak Weekend Peak PM Peak Weekend Peak Year 20200 603 1018 290 363 364 484 Year 2025 702 1153 321 422 433 692 Year 20300 816 1138 354 584 514 967 Safety Expected Accident Reduction at Allen Way None 35% 18% Number of Conflict Points at Allen Way 32 8 32 Access Percent of Diverted Traffic from Allen Way None 26% None Percent of Out-of-Direction Traffic None 18% None 16
CDOT POSITION STATEMENT The history and current condition of the traffic congestion on Founders Pkwy and Allen Way weree born from the lack of coordination between land use and subsequent transportation needs. Specifically, CDOT and the Town have been unfair to the adjacent Allen Way businesss owners by allowing their development to take place without planning a transportation system that would adequately servee these business ownerss and also the residential communities to the east. CDOT is now put in the unenviable position of needing to fix a difficult situation that should have been mitigated long beforee today. It is a well-established fact that an efficient transportation system promotes economic health. Given that, the Town s concern s over lost tax revenue due to access restriction, in the eyes of CDOT, has not been adequately established. The State Highway Access Code states, for proven reasons, that the minimum separation between signalized intersections be 550 feet. The separation between Founders/Allen Way and the Founders/I-25 northbound off-ramp intersections, with the proposed improvements, will be approximately 250 feet. This, in essence, is the crux of the issue. Without the proposed access control at Allen Way, Founders Pkwy cannot reasonably and safely sustain the anticipated future traffic demands. Based on the findings contained in this memorandum, CDOT believes that Alternative 2a does not adequately address the operational and safety improvements for Founders Pkwy and therefore Alternative 2a will require, if chosen; That the Town assumes responsibility for operating all of the traffic signals on Meadows/Founders Pkwy through a Senatee Bill 8 contract agreement. CDOT would also equire that when safety degrades and queuing levels begin to back onto I-25, that access control in the same fashion as Alternative 1a be implemented. CDOT s position asserts that Alternativee 1a is the clear choice in terms of both traffic operation and public safety, has a notably longer design life, and is overall better suited to serve the traveling public and future economic development. 17
Public Open House Attendence Sign in Sheet Number of Attendees Resident 36 Business Owner 25 Public Agency 8 Total 69 Public Open House Questionaire Summary Out of Direction Travel Required? Preference Yes No 1a 2a Neither Where approximately do you live? Meadows 16 6 5 5 Castle Pines 1 1 West Wolfensburger 1 1 Glovey 1 1 Crowfoot 1 1 Sapphine Point 3 1 2 Plainsong 1 1 Woodlands/Blackfeather 2 2 Colorado Springs 3 1 2 Elizabeth 1 1 Metzler Ranch 1 1 Diamond Ridge 1 1 Silver Heights 3 3 Red Hawk 1 1 Happy Canyon 1 1 Parker 2 2 Founders East 1 1 Totals 40 15 19 6 Do you use Founders Parkway to get to and from work? Do you sometimes avoid shopping in this area due to current traffic congestion? Would the proposed access changes in Alternative 1a affect your shopping habits? Would you still continue to shop at the same stores in the area as you do now? Yes No No Response 21 14 5 19 14 7 21 14 5 20 15 5