The Transportation division collects traffic speed and volume data when required for certain projects, for traffic calming-related requests, or when requested by individual citizens. There is currently no on-going traffic counting program underway in Palo Alto, with the exception of turning movement counts which are collected annually for 20 major intersections as part of ongoing monitoring. Engineering and Traffic surveys are conducted once every 7 years on major streets as a requirement to justify the posted speed limits. The last surveys were completed in September 2001.
Speed Monitoring Program
"How fast are people driving?"
This is the million dollar question facing the Transportation Division on a daily basis. In fact, the collection and analysis of vehicle speed data is vitally important for the purpose of understanding, analyzing and improving the existing transportation network. Traditionally, this data is collected using pneumatic rubber hoses placed in the street, or using loop detectors embedded in the roadway. Such approaches are typically location- and/or time-specific, and can therefore be somewhat limited in their ability to collect data. This year, the City of Palo Alto Transportation Division has undertaken an effort to collect more comprehensive speed data throughout the city using an innovative approach - Global Positional System (GPS) technology.
During the spring and summer of 2002, the Transportation Division has collected speed data on the freeways, expressways, arterials, and many collector streets throughout the city using GPS technology. This data has been collected during the a.m. peak hours, the p.m. peak hours, and during off-peak times. Two approaches have been taken in collecting this data, the "maximum segment spot speed" method and the "10-second average speed" method. These two approaches yield somewhat different results and reveal that the answer to the million dollar question often lies in how you interpret the data. There is no right or wrong answer.
The Transportation Division hopes to monitor vehicle speeds using this innovative approach on an annual basis. This monitoring will be used to provide valuable feedback to the Transportation Division, including the ability to observe trends, locate bottlenecks and segments of excessive speeds, and aid in our Residential Traffic Calming Program.
