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Intelligent Transportation Systems (ITS)

What is Intelligent Transportation Systems?

Intelligent transportation systems are a less noticeable but very important technology infrastructure. It applies emerging hardware and software technologies to the challenges of transportation congestion. It is also an effort to provide real time roadway related information to the users in order to improve safety, better travel time and reduce fuel consumption.

Systems utilize different key elements such as countdown pedestrian signal heads, intelligent signal control systems, Dynamic Messaging Signs (DMS), license plate readers, closed circuit TV (CCTV) systems, to more advance applications such as Transit Signal priority, traffic responsive operations, and our traveler’s information web site that uses live data to modify roadway control parameters and provide current information to end users.


Key ITS elements include:

Count down signalThe City of Seattle’s Department of Transportation (SDOT) operates a communication system composed of radio, microwave and fiber optics elements that touch all sections of the road network. It provides radio communications for those maintaining the roads and data transmission for those managing the roads. The data that is transmitted over the system comes from many ITS elements that are part of our overall traffic management efforts.

Count down signals - are used in conjunction with conventional pedestrian signals to provide information to the pedestrian regarding the amount of time remaining to safely cross the street. Pedestrians will use this information to make better decisions about when to enter the crosswalk.

We are able to populate our traffic signals with wireless sensing technology to manage the increase traffic volume data and maximize the efficiency of the roadway. When the volume of both pedestrians and vehicles are low the traffic signal control system can bypass optimized timing routines and operate the intersection to respond to the detected demand.

Dynamic Message sign Dynamic Message signs - are used to give travelers information that can be used in making real time travel decisions. Such information might provide motorist with important information about traffic congestion, incidents, roadwork zones and projected travel times. . These signs may also recommend alternative routes, limit travel speed, warn of duration and location of problem, or simply provide alerts or warnings. Currently, SDOT has four signs that are operational with plans to install 14 more DMS by August 2010.

Traffic Cameras (CCTV) – SDOT currently operates about 56 closed-circuit televisions across the city to help detect congestion and accidents, and to be constantly aware of traffic and road conditions. The up-to-the-minute camera images are sent to our traffic management center for operations monitoring, to the web and dynamic messaging signs for travelers, and to the media. Operators also use the information gathered from the cameras to make operational changes to signalized intersections.

Traffic camera The Traveler’s Information Web site – SDOT’s travelers information website was launched to the public on March 26, 2009.  The map uses an interactive Microsoft virtual background, which uses live traffic data to display traffic conditions both for city arterials and state highways on one map.  Traffic camera images can be viewed by hovering the mouse on camera icons.  Incidents, planned events, and links to other key transportation sites are also posted to the website.

License Plate Reader Systems - uses CCTV technology to scan license plate numbers to measure the travel time along a corridor. The system is set up to have an entry point and an exit point that create a cordon. When a vehicle enters a cordon its license plate number is recorded. If the vehicle goes all the way to the exit point its license plate number is recorded again as well as the time the vehicle took to travel through. This data averaged over many vehicles creates an accurate picture of current travel times. Once the travel time data for a vehicle is recorded the license plate record is discarded.

License plate readers can also be used for road-rule enforcement. Currently, the Seattle Police Department uses this technology at some signalized intersections to issue tickets for drivers running red lights. The intent there is to increase the safety of signalized intersections.

Transit Signal Priority – SDOT currently has a few intersections running Transit Signal priority operations. This system detects buses as they approach signalized intersections. If a bus is detected and the signal is about to turn red for the bus, the signal instead will extend the green light for the bus in an effort to reduce delays for riders. SDOT is currently updating many signal cabinets for the future Rapid Ride Transit Corridors to support this operation.

Traffic Responsive Operation Systems - SDOT will also be implementing traffic responsive operation systems to four corridors for the first time at the end of 1st Quarter of 2010. The traffic responsive operation system is considered one of the most effective operational modes in traffic signal systems. SDOT’s current operation relies on historical data to develop patterns to fit the time of the day needs. Although the methods of using historical data works well for the most part, this breaks down whenever there is an unexpected increase in volume due, for example, to an incident or unexpected detour. In this case the traffic responsive operation system will take into account the volume increase and select from pre-evaluated patterns to fit the needs of the roadway. The traffic responsive operation system will also respond to unexpected low volume by reducing the background cycles to reduce delays.

Traffic Management Center (TMC) - SDOT operates a single Traffic Management Centers (TMC). It is the nerve center for SDOT’s operations activities. Real-time information is gathered from many sources including traffic detectors, CCTV cameras, ramp meters, WSDOT, road crews, incident response teams, and media traffic reporters. SDOT uses this information to coordinate responses to clear accidents, deal with other problems that occur, and notify the public and the media of these events.

Dynamic Message sign

ITS Strategic Plan

This plan provides a 10 year approach for implementing Intelligent Transportation System (ITS) in Seattle.  ITS employ electronics and communications technologies on the street, and automated traffic systems, to enhance mobility for all modes by increasing the efficiency and safety of the transportation infrastructure.
The Seattle Department of Transportation (SDOT) has been implementing ITS for many years, primarily to address mulit-modal (cars, pedestrian, bicycle, transit and freight) operations at traffic signals.  Implementations have included:

  • Enhancing operations by adding communications links, installing new traffic signal controllers with additional capabilities, and increasing the frequency of traffic signal timing updates.
  • Using automated systems that detect congestion and change signal timing to speed traffic  clearance from special event venues (Key Arena, Safeco Field, Seattle Center, Benaroya Hall), from bridge opening, ferry off-loading, and rail crossings.
  • Improving traffic signal operations for all modes by adding detection for pedestrians, bicycles, and vehicles, and by installing improvements to vehicle and pedestrian signal displays, including audible displays for visually impaired pedestrian.
  • Installing and operating transit signal priority (TSP), and other transit systems for buses, streetcars, and light rail trains.
  • Implementing traffic cameras citywide to improve the response to outage and incidents.
  • Providing public area access to traffic information by implementing a website that includes real-time congestion information, traffic advisories and images from traffic cameras.
  • Deploying Dynamic Message Signs (DMS) to provide targeted traffic messages to drivers en route.

The investments and infrastructure in place provide a core set of services.  This infrastructure must be maintained to ensure safe, reliable and efficient operations, and properly managed to realize a positive return on the investment.  This Strategic Plan identifies this, the ITS “Core Infrastructure” as:

  • Traffic signal controllers, cabinets, detections and displays
  • The citywide ITS communications network
  • Traffic cameras that enable staff to view operations and dynamically adjust traffic signal timing if needed
  • DMS that provide on-street traveler information
  • The traveler’s website ( that includes congestion information, traffic advisories and traffic camera images.
  • The Traffic Management Center (TMC) that includes processing, monitoring, and communications equipment allowing staff to interact with the systems.
  • The staff that operate and maintain these assets.


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