Bridge needs four lanes in each direction
June 12, 2008 · Updated 4:44 PM
After reviewing the comments from the Chamber Traffic Meeting held on June 19, its clear the group as a whole has no concept of the gridlock that will occur once the new Tacoma Narrows Bridge is completed and the toll booths are open and operational.
Does anyone really believe the DOT-suggested solutions of adding cameras, ramp metering and graphics will solve the impending disaster? More important than doing studies on a possible new 24th Street onramp is an evaluation of the toll-booth capacity.
Currently, the bridge can handle about 2,000 cars per hour per lane. In the morning, there are certainly more than 4,000 cars per hour trying to get across the bridge eastbound in the morning commute. If it was less than that, the current bridge capacity could handle it.
The best case scenario Ive heard from the DOT is they are hoping for 40 percent transponder usage once the bridge is open. This does not count Sen. Bob Okes assertion that 80 percent will be using transponders.
If you assume 40 percent transponder usage and apply that to the 4,000 cars trying to get across the bridge currently during rush hour, then you can expect about 1,600 cars will free flow across the bridge using the transponder lanes. That leaves 2,400 cars that must pass through the six toll booths. One toll booth lane will be dedicated to trucks, and you can expect that lane to be backed up forever, so lets take that out of the equation, leaving five toll booths for cars.
Lets see, 2,400 divided by five toll booths is 480 cars per booth per hour. Sixty minutes times 60 seconds per minute equals 3,600 seconds per hour divided by 480 cars per hour means each car will have to go through the toll booth in 7.5 seconds in order to accomplish the same throughput as we currently achieve. Does anyone believe that will happen?
If you cant put a car through the toll booth every 7.5 seconds, then pretty quickly the cars will start backing up, first blocking the two lanes that feed in from 36th Street and then out onto the right lane of SR 16.
That SR-16 lane will quickly back up Olympic and Wollochet and the entire community will be in morning gridlock.
The center lane of SR-16 will be blocked by that guy who will try to run up to the front of the line and then cut into the toll booth lanes blocking the center lanes of SR-16, leaving only the outside lane (HOV Lane) as free flow. Unless the HOV guy doesnt have a transponder and has to (at the last minute) try to get across two lanes of traffic to get into line at the toll booth again blocking the right hand SR-16 lane of cars trying to just get past the toll booths.
Then, too, what about those cars trying to exit the toll booth? The right lane of SR-16 will be gridlock again as those five lanes of traffic try to exit the toll both gates all trying to merge into one lane from an almost dead stop.
Thats the bad news. New heres the good news.
We should all be insisting the DOT configure both of the bridges into four lanes instead of three. In the morning, the fourth lane will accommodate the right-hand lane of traffic thats exiting the toll plaza and even the 24th Street on ramp (if approved).
This eastbound fourth lane should continue past Jackson and at least onto the Pearl or even 19th. This will allow for the exiting of about 30 percent of the traffic crossing the bridge before a like amount of traffic is added to the flow from the Tacoma commuters that are entering the system along that stretch of SR-16.
In the evening commute, the fourth lane on the existing Narrows Bridge should extend all the way to Olympic and Wollochet. This will allow another 30 percent of the traffic to exit at these two off ramp leaving two lanes to accommodate the remainder of the traffic beyond those two exits.
The existing Narrows is unsafe because of opposing traffic. With the new configuration, there would be four 11.5-foot lanes all moving in the same direction. It doesnt solve the disabled car problem, but that problem exists all across the state not just on the Narrows Bridge.
This is the only solution to our long-term congestion nightmare that will be foisted on us by this unworkable toll situation. When I recently asked (Narrows Bridge Project Manager) Linnea Laird how the DOT was going to solve this pending toll booth backup problem, she said it had no contingency plan.
This solution should not only be the contingency plan, but should be the plan right out of the blocks. It simply does not make any sense to reduce the current capacity of the existing bridge when we have a capacity shortfall. Without this added lane capacity, we will be in the worst congestion in the state, after the state spent $1 billion to solve the congestion. And to add insult to injury, we still have to pay for it with our toll dollars.
The best part of this solution is will cost almost nothing to implement. The bridges will be in place and they have the lane capacity available. There will be some minor additional shoulder paving required to tie the added lane capacity into the current exit ramps but there are sufficient funds in the contingency fund to pay for that work.
This is the only solution and planning and design work needs to be started now to insure a smooth and workable transition from where we are now to the point where we have real congestion relief. If the DOT is left alone to finish the project as designed we will all be devastated at the results.
I hope when the DOT is done here they will leave us with a better commute than when they started, but without these common sense solutions I simply dont see how that is possible.