Field Implementation of Variable Speed Limits on the Capital Beltway (I-95/I-495) for Woodrow Wilson Bridge Project

The last major construction contract of the Woodrow Wilson Bridge Project was expected to create severe traffic impacts during construction. The I-95/I-495/VA 241 / Telegraph Road interchange reconstruction contract planned to reduce the number of lanes along I-95/I-495 and implement frequent temporary lane closures in order to efficiently construct the over $240 million project. When planning the maintenance of traffic for the contract, the Federal Highway Administration encouraged the use of innovative technologies in work zones to minimize impacts. One such technology is a Variable Speed Limit (VSL) concept which suggests that greater throughput can be achieved if vehicle speed differentials decrease (speed harmonization). A VSL system was implemented along I-95/I-495 to evaluate as a work zone congestion management tool and help mitigate traffic impacts. Near the onset of construction in July 2008, the VSL system became operational but was only active during temporary lane closures on nights and weekends. From May 2009 to January 2010, the hours of VSL activation expanded to include weekday peak periods providing vast amounts of data for evaluation. The VSL system measures of effectiveness included speed, capacity, travel time, queues and delays. Qualitative measures such as public outreach and community feedback were also assessed. This evaluation concludes that successful VSL deployment as a work zone management tool is viable if motorists are informed of work zone conditions, automated speed limit enforcement is used, and if motorists have adequate time to utilize alternate routes, if necessary.