With four months of State Route 16 ramp meter operations behind them, traffic engineers at the Washington State Department of Transportation are ready to take the next step in fine-tuning the ramp meter system.
Beginning Jan. 3, the start times of the ramp meters on the five eastbound SR 16 on-ramps between State Route 302 and the Tacoma Narrows Bridge will change each morning based on live traffic conditions.
Weekday morning traffic demand on eastbound SR 16 will dictate the starting time of the meters, and they could be activated earlier than the static 6 a.m. start time motorists have experienced since metering began on August 30. “We’ve used the first four months to adjust meter cycle rates [the speed at which the lights change red and green] to get the best balance between local traffic and highway traffic,” said WSDOT Regional Traffic Engineer Steve Kim. “The next step is to further optimize traffic flow on SR 16 by using a flexible start time for the ramp meters to help delay the onset of highway congestion. We believe this small change will help people move better through the corridor.”
Kim points to traffic data gathered pre- and post-metering to show how the ramp meters have affected SR 16 traffic flow. His preliminary conclusions are that the meters have reduced the overall duration of congestion in the corridor. Before ramp meter activation, motorists in a typical morning commute would see SR 16 highway congestion start around 6 a.m. and continue until 10 a.m. or 10:30 a.m. With the meters operating, a typical day shows traffic congestion starting about the same time but clearing significantly earlier, between 8:30 a.m. and 9 a.m. The data also indicate that the overall SR 16 corridor speed has increased, thus reducing travel times for motorists.
Another change scheduled to begin in late January will affect motorists using the Olympic Drive on-ramp to eastbound SR 16. Crews will open a second lane on that ramp and operate it as a two-lane metered ramp (similar to how the 36th Street NW eastbound on-ramp is metered). The goal of this change is to help manage the backups on local streets.
Ramp meters are stop-and-go traffic signals placed on highway entrance ramps. They create a short delay between cars entering the highway system, resulting in faster overall travel times due to decreases in collisions at merge points, and a more even traffic flow that maximizes highway capacity.
WSDOT has used ramp meters for years in King and Snohomish counties to manage congestion. Because of their effectiveness, WSDOT has extended their use into Pierce County.
Motorists wanting to see camera images of live traffic conditions along SR 16, as well as throughout the state, are invited to visit WSDOT’s traffic website at http://wsdot.wa.gov/traffic/