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Virginia department of transportation traffic - Fauquier County

Virginia department of transportation traffic - Fauquier County

US 29 / 15 Lee Highway &

US 29 / 15 Lee Highway & Route 215 Vint Hill Road DRAFT Evaluation & Recommendations Install Queue Length Detectors on US 29 NB and DMS Displaying Approximate Distance to Stopped Vehicles This mitigation measure has the potential to allow drivers to react to stopped vehicles before the stopped vehicles are visible to the driver. This measure would rely on queue detectors, a controller, and DMS’s. Different detector types may be used: inductive loop, radar, or video; to detect the back of the signal queue. It is likely that multiple detectors will be installed and there will be gaps between the various detection zones. For example if inductive loops could be spaced every 100 feet. The gaps in the detection zones mean that the detected back of the queue will reflect a shorter queue than there really is. To account for this the controller could assume that the queue is as long as the distance from the stop bar to the first detector that does not indicate queuing. The controller would then update messages on the DMS to reflect the estimated distance from the sign to the end of the traffic queue at the signal. To provide a robust system, redundant detectors and multiple DMS could be installed. This would help to ensure the system remains operational even if a detector or sign fails. However, there would still be potential equipment failures that could compromise the reliability of the system. Drivers would need to interpret the distance to stopped vehicles correctly for this measure to be effective. It is likely that many drivers will not correctly perceive the distances displayed on the signs; however, regular users of the road would likely become acclimated to the distance displayed and the respective queue. This alternative could significantly reduce the number and severity of rear-end collisions on US 29 northbound in advance of the Vint Hill Road intersection. Given the reliance on technology and driver interpretation issues, it is likely that this mitigation measure would not be as effective as some of the concept alternatives at addressing the operational and safety concerns at the intersection. Install a Camera and Full-Matrix, Color, LED DMS This mitigation measure has the potential to allow drivers to “see over the hillcrest”, thereby providing increased stopping sight distance. However, there are number of unknowns regarding the actual design and implementation of this mitigation measure. • What size DMS (video display) would be needed for drivers to view the traffic conditions ahead clearly enough to react appropriately? • Where should the DMS be located for optimum results? • What visual reference markers in the video display are needed for optimum results? • Will the video display distract drivers? • Will the camera and video display require roadway lighting in order to function as desired? • Will one DMS be adequate or will a second sign be required: either for driver perception or technology redundancy and maintenance? • What maintenance issues arise when using a DMS on a 24/7 basis? • What liability issues need to be evaluated and addressed regarding this installation? Given these issues regarding the installation of a camera and full-matrix, color, LED DMS to display video of the traffic conditions beyond the hillcrest, we would recommend that this mitigation measure be pursued only as a research, experimental, or test-bed option. If after research and field test show that this measure can be successfully implemented, then there are quite likely multiple locations through out the state where this may be deployed to enhance the safety of existing roadways. Page 16 of 21 Over a Century of Engineering Excellence

US 29 / 15 Lee Highway & Route 215 Vint Hill Road DRAFT Evaluation & Recommendations Construct Indirect Left US 29 SB to Vint Hill Road This alternative would reduce the northbound queue from about 611 feet to about 165 feet during the AM peak hour which has a longer queue than the PM peak hour. This reduced queue length would provide adequate stopping sight distance for 60 mph traffic on US 29 northbound. Providing adequate stopping sight distance to the back of the queue should significantly reduce the rear-end collisions on US 29 northbound. This alternative would permit channelization of the median at the existing Vint Hill Road intersection. Median crossings could be limited to only left-turns from Vint Hill Road or could also permit the following movements: • through traffic from Vint Hill Road to the commercial entrance, • through traffic from the commercial entrance to Vint Hill Road, and • left-turn traffic from the commercial entrance to US 29 northbound. The traffic models used in evaluating the alternatives reflected permitting all of these movements. If left-turns from Vint Hill Road are the only permitted median crossing movement, then the signal operations and resulting queues would improve, although only minutely. Channelizing the median to restrict median crossings would provide physical reinforcement of the left-turn and U-turn prohibitions for US 29 traffic. The median work should prevent traffic from slowing down and stopping in the left through lanes and eliminate the crashes (six crashes from 2005-2007) involving US 29 northbound left-turns and US 29 southbound traffic. Traffic operations were evaluated at the median cross-over where US 29 southbound traffic would U-turn in this alternative. Based on the modeled northbound 95% queue length of 238 feet and about 1100 feet of sight distance, about 860 feet of stopping sight distance will be available for US 29 northbound traffic – which is more than the required stopping sight distance for even 70 mph traffic. Utilizing indirect lefts for US 29 southbound to Vint Hill Road traffic addresses 72 of the 97 crashes reported from 2005-2007. Rerouting the left turns from the Vint Hill Road intersection, to U-turn at the existing median cross-over does not create any apparent operational or safety concerns at the cross-over. Therefore, this alternative should significantly improve the operational safety of the intersection. Construct Indirect Left US 29 SB to Vint Hill Road and Acceleration Lane This alternative combination would reduce the northbound queue from about 611 feet to about 159 feet during the AM peak hour which has a longer queue than the PM peak hour. This reduced queue length would provide adequate stopping sight distance for 60 mph traffic on US 29 northbound. Providing adequate stopping sight distance to the back of the queue should significantly reduce the rear-end collisions on US 29 northbound. Adding an acceleration lane on US 29 northbound allows a free flow right-turn movement from Vint Hill Road to US 29 northbound. In comparison with the indirect left-turns for US 29 southbound to Vint Hill Road, installing the acceleration lane on US 29 northbound: • marginally improves the queue lengths on US 29 northbound; • eliminates the queuing of right turn traffic on Vint Hill Road; • slightly improves the total network delay; • provides a defined entry location for traffic from Vint Hill Road that should be clearly visible to US 29 northbound traffic; • generates possible weave concerns between traffic from Vint Hill Road and traffic accessing the commercial properties on US 29 northbound; and • addresses the same crash concerns. Page 17 of 21 Over a Century of Engineering Excellence

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