Thursday, November 19, 2009
They appear in the wee hours of the morning and are gone two days later, so unimposing few drivers notice the diminutive devices. But despite their tiny-bump-in-the-road stature, the information they provide affects some of the biggest and most divisive issues – traffic, planning and development – that the local community confronts.
They are the pneumatic road tubes, tiny black rubber lines that stretch across the traffic lanes like a thin, straight black snake making its way across the road. One end of the tube is nailed down to the road, and the other disappears into the bushes where it meets a small box. When a passing vehicle rolls over the tube, the car’s weight squeezes a puff of air to the box, which tallies the number of vehicles traveling on our roadways. Since each axle sends a shot of air, it also counts if the car is a passenger vehicle (two axles) or a heavier-duty freight-bearing truck.
The traffic monitors are placed where data is needed for planning development projects, to anticipate and mediate future traffic needs. The numbers also help city and county officials to keep the roads maintained and dependable under even the heaviest wear and tear.
Each local city conducts its own traffic data counts, as do the Transportation Agency of Monterey County and CalTrans. Since 2007, TAMC has developed a regular testing method, with data collection taking place at peak season (August) and off-peak points (March) over the course of a 48-hour period, between Tuesday and Thursday. Because they missed March due to contracting changes, the off-peak counts for this year are being conducted this month; with tourism slowing during the winter, they anticipate similar numbers to those gathered in March.
Next year, the counts will resume as normal; officials don’t expect big changes from past discoveries. For 2008, the five busiest locations monitored by TAMC for the year were all located on Lighthouse Avenue in Monterey and Main Street in Salinas. At the peak of the tourist season, Main between Highway 101 and West Bernal Drive saw an average of 60,000 cars a day, equal to one vehicle every one and a half seconds for a full 24 hours. Compared to the data from the same location for 2007, that was an increase of almost 15,000 cars per day.
But tubes appear at dozens of other far less trafficked spots – 170 to 200 locations across the county are monitored for the Association of Monterey Bay Governments’ Regional Travel Demand Forecast Model and for CalTrans’ Highway Public Management System.
Mike Zeller is the Associate Transportation Planner at TAMC, and the head of the traffic counts program.
“We collect the data as part of our Congestion Management Program,” Zeller says. “We just keep an eye out and monitor the county roadways to see if there are any hotspots or areas of congestion that need addressing with future improvement projects.”
After TAMC took off-peak reads in 2008, Highway 68 saw some improvements to relieve traffic congestion at the entrance to Community Hospital of the Monterey Peninsula and to make the road safer for patients, visitors and passers-by. Another project is also in the planning stages to further improve access while easing the commute both directions.
This road-count data is also posted online through an easy-to-navigate Google maps. Visitors can choose to display peak or off-peak season data, and then click on individual locations for the numbers. The site also shares up-to-date information about local traffic conditions.
CalTrans frequently uses more advanced pneumatic road tubes than those deployed by local municipalities and AMBAG, and for longer stretches of time, often counting for 24 hours a day for up to a week while recording vehicle weight and speed. This more specific data helps developers project what kind of traffic a new road would face in the future. They can then determine how thick to make the road.
“Do they need a two-lane road? A four-lane road? A freeway?” says Hank Myers, TAMC Transportation Planning Engineer. “When you know what the demands will be, then you can design the pavement, making sure they have a road that’s big enough. All of those things are based on traffic volume.”
The numbers also help developers plan for how thick the roads need to be to hold up to the traffic demands.
“If they need to know how thick to put the asphalt on top and at the base,” Myers says, “they do that by calculating how many vehicles go up and down the road.”
In other words – while few take note that the instruments are tracking our patterns, a lot more drivers would definitely notice if they weren’t.