Traffic Calming

You don't have to be a Traffic Engineer these days to have heard the phrase "traffic calming. But what is traffic calming? In its broadest sense, it refers to the implementation of one or more measures intended to slow down or divert traffic. These measures are normally applied only to local residential streets. As with traffic safety generally, there are three categories of traffic calming, known as the three E's: Education, Enforcement, and Engineering.


Education can consist of measures such as:

  • Meetings and/or workshops with concerned citizens to explain how and why some speeding problems may be more perceived than real.
  • Deployment of the speed trailer to inform motorists of their actual speed and remind them of the posted speed limit.
  • Neighborhood speed watch program to identify neighborhood speeders and apply neighborhood pressure on them to slow down.


Enforcement can include:

  • Utilization of a dedicated traffic enforcement unit (deputy and vehicle) to enforce the speed limit on targeted streets.
  • Use of a traffic enforcement unit in combination with a speed trailer. To be effective, the deputy varies the time of enforcement - sometimes during the use of the speed trailer, sometimes after.
  • Installation of a photo-radar unit that photographs a vehicle's license number and imprints the date, time, speed limit, and actual speed. A speeding ticket is then mailed to the registered owner.


Engineering measures include:

  • Speed humps similar to those constructed on Three Springs Drive.
  • Traffic circles, which are mini-islands in the center of an intersection that force vehicles to drive around them.
  • Chokers, medians, and chicanes. These are various measures intended to encourage motorists to slow down by narrowing or curving the street.
  • Intersection diverters and road closures - relatively drastic measures intended to reduce speeding cut-through traffic.

 When considering the potential application of any of these measures, it is important to learn from the experience of communities that have tried them. For instance, it has been found that some speed control measures are simply not effective. These include stop signs, nonstandard signs such as "Children at Play", and rumble strips. So what are the most effective measures? Based on a survey of over 120 agencies, speed humps provided an average speed reduction of more than 7 mph. This corresponds to our experience on Three Springs Drive, where the speed humps reduced speeds by 7-10 mph. Other effective measures include traffic circles, narrow streets, and use of a speed trailer. Other cities have found that residents are most satisfied with passive measures like the speed trailer and neighborhood speed watch program. Speed humps and chokers come next on the popularity list. 

Should traffic calming measures be implemented in Westlake Village? Residents should carefully weigh the advantages and disadvantages of potential measures. For instance, some measures are simply not attractive, some are expensive, and some may increase City liability exposure. On the other hand, passive measures such as the speed trailer or a neighborhood speed watch program can be relatively easy to implement while still proving effective. If you're interested in discussing the use of traffic calming measures in your neighborhood, feel free to contact the City Traffic Engineer.