October, 2008

Be Aware When the Rubber Hits the Road

By Chris Long

Time flies when you’re having fun, but when trapped in traffic, minutes pass like hours. Perhaps it’s the uncertainty that makes time slow to a snail’s pace when highway congestion makes walking faster than driving. But over the last year, almost 100 digital signs have popped-up around the Bay Area that predict how long, or preferably short, it will take to reach a given destination. These include 20 electronic billboards in San Francisco, such as a prominent one located on the 101 between the Cesar Chavez and Vermont Street exits, which forecasts the time it’ll take you to reach Oakland, SFO, or Palo Alto.

The “Changeable Message Signs” are a collaboration between the Metropolitan Transportation Commission, the California Department of Transportation and two University of California, Berkeley research centers. They display Amber Alerts, accident information and, between 5am to 9 pm, estimated travel times.

“The original intent of the signs was to alert motorists of problems on the road - if a car stalled in lane one on westbound 80, then motorists would know to move over and that their trip would take longer than planned,” said Jeff Weiss, a Caltrans Public Information Manager. “The second step, adding travel times, just helps people make good travel decisions.”

Besides helping people determine when they’ll reach their destination, the signs alleviate surprises from roadway closures, improve public relations, and as part of a larger program of using changeable messages, help reduce congestion, which in turn improves air quality, according to Weiss. For example, if a sign indicates a trip to Oakland that usually takes 20 minutes will take 40, it may prompt drivers to consider taking an alternative route, pulling over and enjoying a cup of coffee, or even returning home instead of inching through gridlock.

Caltrans makes the predictions by timing cars as they travel between two points using sensors embedded below the highways surface that track vehicle flow, as well as from roadside “transponders” that monitor vehicles equipped with FasTrak.

UC Berkeley’s contribution was creating the software that sends the information to the signs. “Travel time is recalculated every minute, and an update to the sign is made whenever the time changes by two minutes,” said Alan Chow, who supervises the project for Caltrans.

Some meticulous motorists have taken it upon themselves to test the accuracy of the predictions. “When I travel to Palo Alto from the City I’ve noticed that most often the two signs I pass say that Palo Alto is 16 minutes away, then eight,” said Donald McCasland, a software engineer and San Francisco to Palo Alto commuter. “When it has changed, I’ve been interested enough to time it, and they were spot on.”

I too tested the signs’ precision. My test drive started at the electronic sign located on Highway 101 just before the Vermont Street exit. It told me that it’d take me 19 minutes to reach Oakland. The trip actually took 20 minutes, but what’s a minute, give or take?

UC Berkeley recently conducted a survey of people’s reactions to the travel time signs. “We had very positive responses,” said J.D. Margulici, a Senior Development Engineer at the California Center for Innovative Transportation, a university research center. Eighty percent of survey respondents felt that the posted destinations were suitable, and almost everyone praised the signs’ accuracy.

Margulici noted that the survey didn’t question commuters about alternative routes. “In reality most itineraries in the Bay Area don’t have that many options” said Margulici, “perhaps alternative routes are not realistic due to California’s infrastructure.” He did contemplate the possibility of adding alternative route suggestions in the future.

According to Weiss, the only complaint Caltrans has received about the signs was about their expense. But he explained adding the travel times to the existing alert signs “barely cost anything” – just $50,000 – since the rest of the technology was already in place.

For some travelers these funds have been well spent. As one survey respondent stated, “Estimated time, no matter how long, reduces travel anxiety.” In an era where time is far more capricious than money, travel time signs may be one dependable prediction in an increasingly unpredictable world.