902.16 The Mobility Plan – Effective Arterial Management

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Support. The Mobility Plan, a focus on effective management of arterials, supports the MoDOT Tracker tangible result of uninterrupted traffic flow. Specifically, this plan focuses on improving the performance measure for the arterial system, Average Rate of Travel on Selected Signalized Routes. Strategies to improve the operation of signalized routes are provided.

With more than 2400 signalized intersections across the state, Missouri has a challenge to keep traffic moving as efficiently as possible along the arterial system. A recent self-assessment showed management, operation and maintenance of Missouri’s arterial system rated a D. While this is slightly above the national score of a D-, we have not focused enough resources in this area.

Each district has developed a district mobility plan to study each of their arterial systems. Each mobility plan will focus on making significant improvements to all arterial systems. As part of the mobility plan, districts will perform before and after studies that should show these improvements.

Standard. District mobility plans were implemented on January 1, 2009 and shall be completed within five years (January 1, 2014).

Support. Signals are a large investment in our transportation system, spending approximately $8 million a year installing signals and $10 million a year in maintenance. Signals can also cost the public money through increased travel times and crashes and decreased air quality. Signal retiming costs an estimated $3,000 per intersection with a benefit/cost ratio of 40:1. With regular signal timing updates, maintenance and repair, we can reduce travel times by a projected 8% to 25%.

Signal timing is not the only component of uninterrupted traffic flow. Intersection design and access management also play an integral role. With poorly spaced signals and insufficient intersection designs, even the best timing plans are not effective in moving traffic. Signals must be designed to accommodate future growth, large vehicles when needed, pedestrians and consider signal operation. Installation of new signals must also consider the existing signals and how well one will fit with the rest, not just focus on volume, but coordination as well. Access allowed within the functional area of a signalized intersection can reduce the efficiency of the signal to move traffic. Signalized intersections with access control function 30% to 50% better than those without. This improvement in access can also increase the level of service of the corridor.

The Mobility Plan is not only meant to focus on improving uninterrupted traffic flow but also has benefits for reducing accidents and providing a safe transportation system. Over a three-year period, 2004 – 2006,146 fatalities and 2,471 disabling injuries occurred at signalized intersections. By updating signal timing, a 10% reduction in all accidents could be expected and interconnecting signals a 15% reduction in all accidents with a 29% reduction for fatal and injury accidents specifically.

The Mobility Plan presents strategies to improve areas of signal operations, design and access management. It is not expected for each district to focus on every one of the strategies listed. Instead, this is a compilation of ideas to consider and implement those that will improve uninterrupted traffic flow for an area within budgets and resources. Districts can also go beyond these strategies. Decisions will have to be made and this document can help guide those decisions, direction and development of each district plan.