FAQ: Ramp Meters and Eastbound State Route 16

What effects have ramp meters had on SR 16 traffic?

In November 2005, WSDOT traffic engineers gathered preliminary traffic data to look at the effects of ramp meters on SR 16 traffic. Here are their findings:

1. The inital plan for ramp meter operations was to keep them activated on weekdays until 10 a.m. based on the duration of traffic congestion observed during the "before ramp meters" condition. What we have found, however, is that the operating meters have reduced the duration of morning traffic congestion and the time traffic needs to return to a "free flow" condition. That means we are able to turn off the meters between 8:30 a.m. and 9 a.m. (based on location of the ramp) as opposed to the 10 a.m. original time.

2. At the same time, we have noticed that bad weather (rain, fog, etc.) reduces SR 16 capacity by almost 10 percent. When a highway operates at or near capacity (like SR 16 does virtually every weekday morning), this 10 percent reduction makes a big difference and extends the congestion period significantly. On bad-weather mornings, we occasionally need to run the meters past 10 a.m.

3. Preliminary "after ramp meters" data indicate the meters delay the onset of congestion. Because of the shortened congestion period, we compared a driver's average speed each hour between 6 a.m. and 10 a.m. on eastbound SR 16 near the eastbound merge at the 36th Street NW on-ramp. The four average speeds after ramp meters all increased to around 31 mph (compared to 20 mph before the meters were activated). We believe this is a remarkable improvement in highway function directly related to ramp meters.

What is the next step for metering SR 16?

WSDOT has begun varying the start times for the SR 16 ramp meters. This recent news release explains how and why this change has occurred.

Why did WSDOT install ramp meters on State Route 16?
For years, eastbound SR 16 has experienced chronic backups during the weekday morning commute. Together with the TNB Project, several roadway improvements are occurring on SR 16 with the goal of adding capacity in the corridor between Union Avenue in Tacoma and Olympic Drive in Gig Harbor. Motorists will see capacity increase in peak commute directions in spring 2007. Permanant capacity improvements will be in place in spring 2008, and they will extend beyond the project itself and go from Olympic Drive in Gig Harbor to Union Avenue in Tacoma. Construction activities related to the new Narrows Bridge, namely temporary narrowing of lanes and shoulders, reduces the vehicle volumes that normally travel through the corridor, and making peak-hour congestion worse.

As we build new corridor capacity, it is possible to manage another element of congestion: traffic demand. Ramp metering is a proven tool to both improve safety and optimize the carrying capacity of a highway corridor. On SR 16, the majority of morning traffic approaching Tacoma Narrows from the west during weekday commutes enters the freeway at five on-ramp locations: SR 302 (in Purdy), Burnham Drive, Wollochet Drive, Olympic Drive, and 36th Street.

Why were SR 16 ramp meters installed at every ramp as far west as SR 302?
Metering eastbound ramps is essential for effectively managing traffic demand and flow in the corridor. This is a corridor-wide, not a ramp-by-ramp, strategy. Eastbound traffic volumes, coming from as far away as SR 302, have a significant effect on the overall operation of this corridor.

Does the installation of ramp meters mean WSDOT has concluded the TNB project will not improve the flow of traffic on SR 16?
We fully expect that the completed corridor improvements will enhance the flow of SR 16 traffic. The installation of ramp meters is serving commuters by optimizing the flow of traffic that leads to and travels through construction work zones.

Will these ramp meters eliminate the backups on SR 16?
These ramp meters will NOT eliminate backups on SR 16. The traffic demand exceeds the capacity of today’s highway by more than what meters can manage. We have found, however, that the ramp meters reduce the length of backups, reduce the overall time the highway is congested, and provide travel time savings along the corridor.

Will these ramp meters be removed after the SR 16 construction is complete?
The meters at 36th Street and Olympic Drive are permanent systems and will remain after construction is complete. The meters at Wollochet, Burnham, and SR 302 were installed as temporary systems. Once the new bridge is complete in April 2007, the continued use of meters west of Olympic Drive, largely will depend on the percentage of peak traffic that uses electronic tolling. If a large number of drivers (more than 50 percent) choose to pay the bridge toll by cash, it may well be necessary to operate the meters to manage traffic demand.

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