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Traffic Surveys

Transportation and Public Works is now Sonoma Public Infrastructure - Website updates coming soon!

Average Vehicles Per Day

ADT Color Ramp - 300x16

85th Percentile Speed (Miles per Hour)

MHP Color Ramp 1
30 or Less 45 or Higher

Traffic Count Metrics

Average Daily Traffic (ADT)

This measure indicates the average number of vehicles that travel a specified road location within a 24-hour time period. This metric is also referred to as Volume or Vehicles Per Day (VPD).

Most County roads are have two travel lanes: Northbound and Southbound, or Eastbound and Westbound. Volume is indicated as a total for both travel lanes, as well as for each lane individually.

AM & PM Peak

These measures indicate hours that peak traffic volume occurs, as well as what the traffic volume is during those hours. Times are listed in 24-hour clock format, and the hour listed indicates the beginning time. For example, 209 @ 0700 means that there were 209 vehicles counted between the hours of 7:00 and 8:00 AM. 144 @ 1400 indicates that there were 144 vehicles counted between the hours of 2:00 and 3:00 PM.



Speed Survey Metrics

85th Percentile Speed

The 85th Percentile Speed is the speed at which 85 percent of drivers travel. This is the generally the recommended and enforceable speed limit.

Established Speed Limit

The Established Speed Limit is the existing speed limit, or the speed limit that was set based on the 85th Percentile Speed.

Radar Date

The Radar Date is the date that the speed survey was taken.

Certification Date

The Certification Date is the date that the speed survey is reviewed approved by the managing Civil Engineer.