Effective sometime this March, all five of the on-ramps to eastbound State Route 16 will be metered. That includes the (Purdy) State Route 302, Burnham Drive, Wollochet Drive, Olympic Drive, and the 36th street on-ramps. There won’t be any meters westbound.

Ramp meters, if you aren’t familiar with them, are stop-and-go signals located on entrance ramps to a freeway. They look a lot like traffic lights. The purpose of the meters, according to Claudia Cornish, communications manager for the Tacoma Narrows Bridge project, “is to keep traffic flowing during the morning eastbound commute.”

“They do that by regulating the rate by which cars enter traffic,” she said.

Things to know about ramp meters
Pull your vehicle up the white line
(stop bar) to trigger the ramp meter.
On average drivers wait less than
two minutes during peak hours.
By increasing the efficiency of
freeway use, ramp meters save money that would otherwise be spent
constructing additional lanes.
Past ramp meter activations have
reduced rear-end and sideswipe collisions by over 30 percent.

Ramp meters are being used in more
than 20 cities and 12 states in the
United States.

Information provided by WSDOT.

According to information supplied by the Washington State Department of Transportation, “A ramp meter consists of two components: a traffic signal and a ‘loop detector’ or traffic sensor.” The loop detector senses when a vehicle passes over it, and sends that data to the state’s Traffic Management Center in Tacoma, where a computer determines the proper interval for that particular ramp. Because television cameras will be installed at each of the five interchanges, engineers will be able to monitor the situation and override the central computer should that be necessary. The meters will come on only as they are needed, so unless traffic happens to be especially congested on a particular weekend, they will be off. Installation of the meters comes in response to input from surrounding communities, which requested that WSDOT find ways to mitigate congestion resulting from the new Narrows Bridge project.

Cornish explains the increased congestion this way. “Standard capacity for a freeway or a state route is about 2,000 cars per lane, per hour, based on standard widths. The normal lane width is 12 feet—and the normal shoulder width is 8 feet on each side. At the moment those lanes (in the area where construction is taking place) have been reduced to 11-foot-wide lanes and 2-foot shoulders.” So, friction increases as both lanes and shoulders narrow, thereby slowing traffic. Or, in the case of an accident, can bring traffic to a complete halt since there isn’t enough room to pull off the road.

The cause of the congestion is what Bill Elliott, civil design review manager for the Tacoma Narrows Bridge project, refers to as “common sense.” But computer modeling confirms the problem, and “of the five entry points between Purdy and the Narrows bridge, the entering volumes are highest from SR-302,” he said.

When asked if the meter on the Purdy on-ramp will create backup problems, Elliott acknowledges that there will be a line to get on the freeway, “but by no means will the queue come back so far as to adversely impact the signal in Purdy.”

So what’s in it for you? Well, that depends on how frequently you travel to the bridge. According to data provided by WSDOT, the average travel time to the west end of the Narrows Bridge for a commuter entering SR-16 via the Purdy/SR-302 on-ramp is 21-minutes and 12-seconds. After the meters have been installed and activated, engineers expect that time to drop to 20 minutes and 24 seconds. A savings of 48 seconds per trip! That doesn’t sound like much, but had you commuted to Tacoma on each working day of December (not counting holidays) the total savings would have added up to a whopping 1,104 seconds! That’s more than 18 minutes, which would be nice to get back. And, if you make the trip more often, the savings will be even greater. Of course the real benefit consists of the theoretical 48 seconds multiplied by thousands of commuters. And that, it seems fair to conclude, will amount to a really substantial improvement.

Plus, there’s a potential psychological savings as well, since most of us feel less stressed when traffic flows smoothly (if slowly). And, according to Elliott, all of the ramps between the bridges and Interstate-5 will eventually be metered.

One more thing. For those of you who simply don’t have the time to wait in line at the local ramp meter, you can go ahead and blow through, but the Washington State Patrol will charge you $101 for the privilege.

For more information, go online to www.tacomanarrowsbridge.com.

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