Almaden Expressway Traffic
by Bob Boydston, AVCA Past President
Updated February 2010

 

Traffic is one thing that residents of Almaden Valley share in common, and we are very aware of changes in traffic congestion.  Almaden Expressway is the principal roadway in Almaden Valley.  There are ten major intersections along the expressway, from Blossom Hill Road to Harry Road.  The busiest of these intersections are Blossom Hill Road, Coleman Road, and Camden Avenue.

Traffic engineers use automatic data gathering from the transmissions of test cars and a computer program to come up with a descriptive status of traffic conditions.  The output of this program is called the Level of Service (LOS).  These levels are described with designations "A" through "F", with "A" being the best and "F" being the worst.  The measurements are usually taken during the busiest two hours of peak use, for instance, from 4:00 PM to 6:00 PM on weekdays.

    LOS:  Wait times at intersections at peak hours under the 1985 Highway Capacity Manual
      A 0 to 5 seconds
      B 5.1 to 15 seconds
      C 15.1 to 25 seconds
      D 25.1 to 40 seconds
      E 40.1 to 59.9 seconds
      F 60 seconds and more

Now let's look at a more detailed description of LOS.

      LOS Vehicle Delay in Seconds Volume to Capacity Ratio  
      D 25.1 - 40.0 0.80 - 0.89 Approaching Unstable, Tolerable Delays:  Drivers may have to wait through more than one red signal indication.  Queues may develop, but dissipate rapidly, without excessive delays.
      E 40.1 - 60.0 0.90 - 0.99 Unstable Operation, Significant Delays:  Volumes at or near capacity.  Vehicles may wait through several signal cycles.  Long queues form upstream from intersection.
      F 60.0 N/A Forced Flow, Excessive Delays:  Represents jammed conditions.  Intersection operates below capacity with low volumes.  Queues may block upstream intersections.

The National Standard for minimum satisfactory traffic congestion is Level of Service "D".  LOS "D" is recognized by the City of San Jose as the minimum acceptable level of service.  In the 1985 Highway Capacity Manual (Transportation Research Board, Washington, D.C.), the next level down, LOS "E", is called "extremely unstable, driver comfort poor, average traveling speed 28 mph for a 50-mph-designed expressway, and minor incidents causing serious breakdown with extensive queuing."  In 1988 there were two San Jose intersections at LOS "F".  In February, 2004, there were fifteen at LOS "F".  The worst intersection was Montague/Trimble where the average rush hour delay was 270 seconds.

The LOS levels above were measured as the time that a vehicle was stopped at a red light.  In 2004, the method of calculating the LOS values was changed to include the time of deceleration to a stop light plus the time to accelerate after the light turns green in addition to the wait time at a red light.  This has resulted in improved LOS levels for the same amount of traffic.  The new LOS calculations are based on the 2000 Highway Capacity Manual calculation method replacing the previous 1995 Highway Capacity Manual calculation method.  Under the new method of calculating the LOS, the last values for Almaden Expressway intersections are:

      LOS values in 2006
      Camden Ave. D
      Coleman Rd. D
      Blossom Hill Rd. E

Under the new method of LOS calculation and with the reduction of employment, Blossom Hill Road has met requirements, although when it is driven at rush hour, for the public, an LOS "F" gridlock impression remains.  In the Transportation 2000 Report, it was suggested that a grade separation be constructed at Blossom Hill Road, but the cost has discouraged the County from considering it.

Almaden Expressway is under the jurisdiction of the Santa Clara County Traffic Authority.  The other roadways in Almaden Valley are under the jurisdiction of the City of San Jose Department of Streets and Traffic.

Housing development in Almaden Valley is totally under the control of the City of San Jose.  However, the county can request that the city require developers to make improvements to Almaden Expressway to mitigate any new traffic caused by their developments.  In addition to Almaden Expressway, the county controls seven other expressways, two of which are Capitol and San Tomas Expressways.

Planned Improvements for the Almaden Expressway.  These plans are on hold due to County budget problems.

      Widen to 8 lanes between Coleman and Blossom Hill including additional South Bound, (SB), left-turn (a total of three) and through lanes at Blossom Hill, a 4th SB and NB through lane at Via Monte, and additional SB, EB, and WB left turn lanes, and WB right-turn lane at Coleman

      Widen to 6 lanes starting south of Camden to conform with the existing 6-lane segment south of Redmond with additional EB and WB left-turn lanes at Camden.

      Widen to 6 lanes from Almaden Road to south of Camden.

It was mentioned above that LOS "D" is recognized by the City of San Jose as the minimum acceptable level of service.  According to 1999 data, during peak hours (generally between 7 AM and 8 AM, and between 5 PM and 6 PM), 64 percent of San Jose's freeways and 18 percent of expressways were at LOS level "F", and 7 percent of local streets were at LOS level "E" or "F".  It would be interesting to see more recent data on the LOS levels for these various types of streets.