Simulated photo of I-405's proposed two-lane express toll system. Enlarge photo.
|Traffic in 2032|
Over the next 25 years, projected increases in population and jobs for the central Puget Sound region will worsen today’s gap between transportation demand and capacity. If the trend continues, commuters could spend 300 percent more time sitting in traffic. A recent study projecting central Puget Sound traffic congestion under current traffic models in 25 years predicts:
• 1.1 million hours of traffic delay per day
• 40 percent more vehicles
• Deteriorated traffic flow in all corridors with an average of nine hours of congested traffic conditions daily along heavily traveled corridors.
|Overhead gantries on England's M42 near Birmingham display variable speed limits over each lane and can close lanes in the event of an emergency.|
|This conceptual rendering illustrates how ATM tools, such as overhead gantries with variable speed limits and driver message signs, could help ease congestion on I-5.|
WSDOT is entering a new era in fighting congestion and improving safety. New technologies that more evenly distribute traffic and alert drivers of problems down the road are redefining how we manage our highways. At the heart of all this new technology is the ability to adapt to constantly changing highway conditions and respond in the most efficient manner - we are working on making our highways smarter with new techniques and tools. Some of the new tools include:
Building smarter highways through active traffic management
Smarter highways, or active traffic management technology, or ATM, as it is called in the industry, dynamically controls traffic based on real-time roadway conditions. Using integrated systems and a coordinated response, both every day and incident-related congestion can be managed to improve roadway safety and traffic flows.
WSDOT is studying ways to improve traffic flow and testing new techniques to manage traffic on the region’s busiest routes. New smarter highways tools that soon could help reduce congestion here include:
- Overhead gantries -will display changing speed limits and real-time traffic information for drivers over each lane.
- Variable speed limit -will dynamically and automatically reduce speed limit signs so drivers are alerted to slow their speeds when they approach congestion, collisions, or backups at off-ramps.
- Queue warning - alerts drivers of downstream backups and directs drivers passing through to use alternate lanes.
- Junction control - uses changeable traffic signs, electronic pavement markings, and lane use control to direct drivers to use specific lanes (mainline or ramp) based on varying traffic demand.
- Hard shoulder running - this technique increases traffic flow by allowing drivers to use the shoulder as a traffic lane during the most congested periods or to move around a collision or stalled vehicle.
- Dynamic rerouting - this tool uses overhead signs, lights and changing lane markings to alert drivers that they need to change their route based on current traffic conditions.
- Travel time signs -These signs display estimated travel times and other traffic conditions so drivers can take more control over their commutes and make on-the-road route decisions.
High occupancy toll (HOT) lanes give drivers a new choice and make highways more efficient by allowing just enough additional traffic into underused carpool lanes. An electronic toll that fluctuates with the level of congestion lets solo drivers use carpool lanes reserved for vehicles with two or more occupants. The dynamic pricing keeps the HOT lane free flowing while reducing congestion in the general purpose lanes. The state’s first HOT lanes will begin a four-year test period on SR 167 between Renton and Auburn this spring. There are six HOT lane facilities successfully operating in other states and several others are in development.
Express Toll Lanes
In the not-so-far-off future, WSDOT might use other forms of congestion pricing like HOT lanes on highly congested freeways, such as I-405. Express Toll Lanes would offer an escape from congestion with an electronic toll that fluctuates with the level of demand. The result would offer commuters more choices and help reduce congestion in all the lanes.
Tolling and variable tolling can be used to manage the amount of traffic in a lane or on a roadway. WSDOT’s Good To Go! electronic tolling system allows users to pay a toll without stopping at a toll both. Tolling also could help pay for vital capacity improvements, such as those planned for the SR 520 corridor.