The in basket: I first saw the overhead electronic signs telling me how many minutes I am from an upcoming destination in Las Vegas, and now I see them along I-5 on the other side of the Sound.
“They are a nice amenity,” I wrote to my state highways contact, “but I doubt they would be worth their cost if that was all there is to it. What function do they serve for traffic movement?” I asked.
The out basket: Jamie Swift, the contact, replied, “Our travel times posted on area electronic message signs change as congestion increases or decreases. The travel time are calculated by a computer that uses electronic vehicle detectors located underneath the roadway. These are the same traffic detectors that provide drivers, the WSDOT Web site and the media with congestion information.
“How are these tools valuable?” she asked, rhetorically. “They help drivers on the road choose alternate routes. For example, a driver traveling to Everett has several choices if there is a collision ahead blocking two lanes of northbound I-5 just north of SR 520 during the peak afternoon commute.
Assuming the driver is just south of the I-5/I-405 interchange in
Renton, the driver can choose to take I-405, SR 520 or continue on their
journey on I-5. The travel times on the highway can show the driver
which route is the fastest way.”
The signs are backed up by a Web site that allows a driver to go online to calculate his commute times to various destinations, offering what it calls an accurate estimate 95 percent of the time based on 2006 travel date. You can give it a try at
http://www.wsdot.wa.gov/Traffic/Seattle/TravelTimes/95reliable.html
They are also psychologically calming since they let you know what to expect. Like the signs at Disneyland that have wait-in-line times on them.