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Dynamic Speed Display Devices

A Dynamic Speed Display Device (DSDD) measures and displays the speed of vehicles approaching the face of the device. Typically, a speed limit sign is included with a DSDD to advise drivers of the speed limit at that point on the roadway. The Rotating DSDD Pilot Program is intended to be another tool in the ATD traffic engineering toolkit for ongoing speed monitoring.

Photo of Dynamic Speed Display Device.

What is a Dynamic Speed Display Device used for?

DSDDs are typically used to encourage drivers that are traveling faster than the speed limit to reduce their speed in neighborhoods and construction zones. Both portable and fixed-location DSDD units are available. Portable units are typically placed at a location on a roadway for a relatively short time period and then relocated to a different location. Fixed-location units are used for the long-term display of vehicle speeds at a given location. These guidelines address the installation of portable DSDDs in the City of Austin.

What is the Rotating DSDD Pilot Program?

The Austin Transportation Department launched the Rotating DSDD Pilot Program in September 2016 when it began deploying six portable DSDD units at various locations around the city, based on citizen complaints and other community input. Each DSDD unit is left in place for four weeks at a time, during which it collects real-time data on vehicular speeds and volumes. The data is stored in an online web portal and can be accessed to generate custom reports and understand driver behavior. After the four-week deployment is over, the DSDDs are moved to a different set of locations. The DSDD rotation list is developed on a first-come, first-serve basis based on citizen complaints.

The Rotating DSDD Pilot Program is being implemented to allow a limited number of DSDDs to be installed and monitored for a limited time frame (four weeks) to determine whether or not they are effective in the long-term reduction of speeds on streets with documented speeding. Data from the DSDD units can be used for more effective and targeted enforcement activities. A 2012 research report by the Morgan State University National Transportation Center (Baltimore, MD) concluded that, while DSDDs are effective, their effectiveness reduces with time. The research team also concluded that a DSDD is effective only for a short distance, as drivers increase their speed after passing the DSDD.

What are the criteria for DSDD installation?

Before requesting a DSDD, please read the Installation Criteria Guide to determine whether a certain location can be considered as a candidate for DSDD installation.

How can I request a DSDD?

Please contact Austin 3-1-1 to request a DSDD deployment on your street.


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