Active Traffic Management (ATM) is cutting edge (at least in the US) implementation of Intelligent Transportation Systems (ITS). So then what is ITS? ITS is the application of technology (sensor, communication, processing, and dissemination) to the transportation field. It is an umbrella term that includes many specific technology such as Transit Signal Priority or Advanced Parking Management Systems.

WSDOT has been a nationwide leader in ITS infrastructure. Everyone should be familiar with the FLOW map, has read  Variable Message Signs (VMS) and has been stopped by ramp meters (unless you take transit or carpool). The HOT lanes on SR-167 and the Tacoma Narrows Bridge are applications as well. ITS and traffic management systems like incident response units have been an indispensable tool for WSDOT to reduce congestion and improve travel time reliability.

Causes of Congestion
Causes of Congestion

The problem with all of these tools is that they respond to traffic congestion rather than actively try to manage and reduce congestion. This is were the active in ATM systems comes from. A majority of non-reoccuring congestion is caused by incidents and car crashes. The major objective of ATM is to reduce the number of crashes and significantly reduce the number of secondary crashes. This shrinks the 25% or so of congestion caused by incidents and has an added benefit of improving safety. This is accomplished by reducing speed limits when free flowing cars are approaching a backup or the freeway is close to its capacity. This strategy is also used when a crashes create a backup. This is the main focus of WSDOT’s first ATM project on I-5 NB from Boeing Access Road to I-90, and will eventually include both I-90 and the SR-520. More ATM strategies identified by FHWA are:Speed Harmonization,Temporary Shoulder UseQueue WarningDynamic Merge ControlConstruction Site ManagementTruck RestrictionsDynamic Rerouting and Traveler InformationDynamic Lane Markings, and Automated Enforcement. The photo below shows most of these strategies in action, with the associated system components.

ATM on the M42 in the UK
ATM on the M42 in the UK

Another benefit of ATM is the ability reduce speed limits so that hard running shoulders (think SR-520 HOV lanes west of Bellevue Way) can be used during peak periods. The reduced speed limits are neccesary to maintane safe operations due to the lack of shoulders. I’m not completely versed on R8A but I think this is how WSDOT got the FHWA to agree to the lack of complete shoulders along I-90. WSDOT has a good folio with a lot of the same information.

UPDATE – Here is an interactive page that the Highways Agency in the UK made for the M42.

24 Replies to “What is Active Traffic Management?”

  1. Not the same thing, but I thought I’d throw this out there, in case you hadn’t heard of it.

    I lived in the UK for a couple years, and while I was there they installed “average-speed cameras” on the A14 between Cambridge and Huntingdon, which just happened to be my morning commute. The idea was that the first camera you crossed would note your license plate number, then as you passed each subsequent camera the system would calculate your speed between the two, and if it was higher than the speed limit, it would ticket you by mail. Overnight, it became impossible to speed without getting caught. Also overnight, the road went from being an incredibly congested, stop-and-go nightmare to being a busy but free-flowing highway as everyone was forced to obey the speed limit. I couldn’t believe how well it worked, and traffic accidents dropped by half. Obviously it has its detractors, but I thought it worked very well.

    1. I wonder if that is legal in the US. I think that red-light cameras, which have photographic proof of law breaking, are on sort of shaky legal grounds. The right to face your accuser, no proof of which driver made the fault just which vehicles, and privacy issues. This would be one step further.

      1. There have been some similar issues in the UK. Some people manage to get out of the speeding tickets by arguing that the police have no evidence of who was driving the car at the time, and there have been challenges based on privacy law. The thing is that most people who get fined pay, and that’s enough to change the majority of peoples’ behaviour.

        The average speed cameras are almost universally unpopular with drivers, but I think Derek’s observation about their effectiveness applies pretty generally, whereas the old-style point speed cameras caused a lot of abrupt slowing down and speeding up because people knew where they were.

      2. Yes it is very important to ensure that laws relating to speed cameras are very well written so that when they are challenged in court the state wins. I went to a house transportation committee meeting where this was a significant part of the discussion.

        Sweden has a large number of speed enforcement cameras. When I was there last summer we drove along a country road that had them every 5 miles or so. They certainly make people slow down because everyone know that if they speed past them they will get a ticket. Thing is that everyone speeds up between them. Our GPS unit even gave us warning when we were speeding at approaching the cameras. I know it sounds nannyish but then again Sweden has the first or second the safest roads in the world.

      3. The way we usually get around that type of stuff is by using cameras just to issue a civil ticket, rather than a criminal one. If you run a red light, for example, I think they just send a fine to the owner of the car since they can’t prove that the owner was actually driving, which they would need to do in order to issue a criminal ticket. Camera infractions don’t show up on your insurance, for example (although this is just what I’ve read, cause I’ve never gotten one). It’s the same way you can get a parking ticket on your car even though the government can’t prove you were actually the person who parked it.

  2. I should mention WSDOT recently implemented ATM in the form of a new shoulder along the US 2 eastbound trestle, east of Everett, that also acts as a third GP lane during peak-commute hours.

    1. Are there automated signs for that? If not, it is not active, it’s just signs posted saying you can use the lane during certain hours which is what they did on the SR 302 off ramp from SR 16 westbound due to congestion at a traffic light.

  3. Glad to see that WashDOT is looking at doing what the Netherlands has done on its limited-access divided highways…20 YEARS AGO!!!!

  4. What about variable speed limits on a lane-by-lane basis? It’s an intriguing idea, but could be potentially dangerous without lane-change restrictions. Think temporary express lanes: when conditions allow, the inner two lanes are hiked to 70, while the outer two lanes remain at 60. Cars wishing to enter those lanes can do so only at the entrance point and must maintain the higher speed while in those lanes. (No trucks in those lanes might be a nice kicker.) During that stretch, drivers can leave the high-speed lanes to exit the highway, but not re-enter them (creating an advantage over current HOV or express lane systems). These lanes would not have dedicated exits. At a reasonable point, all lanes return to normal speed.

    Either that, or expand commuter rail.

  5. The UK site is sweet. Nothing else to say since I drive on the freeway maybe twice a year at most…

    1. I wonder how “regular” drivers would react if ATM was implemented. I say this because there seem to be a lot more stupid drivers who can’t comprehend even the simplest signs, like “DON’T CROSS DOUBLE-WHITE LINES” or “KEEP RIGHT EXCEPT TO PASS.” What would happen if these dumb drivers were confronted with all those new signs and rules?

      1. It would be complete carnage. I was waiting at the Eastgate freeway station last week and was amazed at how many SOV’s were using the HOV ramp to access I-90, and then proceeding to cross the double-white to get to 405. Are simple rules really that hard to follow? There was even a trooper there watching the ramps. I saw several people start down the ramp and then turn around behind the trooper so they wouldn’t get caught!

    1. Not on the I5 segment but it will be part of the tolling system on SR520. ATM can stand on it’s own and does not need tolling systems.

  6. These signs are excellent and hopefully they will work just fine. Like Derek above I am from the Uk and variable speed signs were used on the M25 motorway around London – at least on sections of it around Heathrow Airport if I can recall correctly. I was much younger then, but they seemed pretty effective and in your face so you couldn’t miss them.

    Good work, WSDOT. Now if they only add improved signage for SeaTac Airport on the I-5, I-90 and I-405 and ‘cats eyes’ (embedded lane reflectors), I would be quite happy! That’s another tale however and perhaps not for this post.


  7. This article by Adam Parast is a very interesting summary.

    What I like about Active Traffic Management is that it can be designed to provide appropriate priority to bus transit in congested conditions. Potentially part of integrated corridor management (ICM).

    More than you want to know about ICM is posted by US DOT at http://www.its.dot.gov/icms/index.htm .

  8. Obama Administration seeks input on intelligent transportation systems. An opportunity to request an emphasis on transit applications.

    If you’ve never commented on a Federal docket, you ought to give it a shot; it’s participatory democracy.

    New RFI: U.S. DOT Requests Public Comments on ITS Program


    Category > Opportunity: April 22, 2009 (JPO)

    The Research and Innovative Technology Administration (RITA) is requesting public comments through a Request for Information (RFI) on the strategic direction of its Intelligent Transportation Systems (ITS) Program. Comments will be used to shape the next, multi-year, ITS research agenda. Specifically, the Department seeks comment and insight on a set of proposed goals and objectives for the ITS Program. The content of the RFI represents the current thinking on the next strategy for ITS Program research, a strategy that is under development and will be reflected in an ITS Program Strategic Plan that is expected to be completed in October 2009.

    The department is interested in exploring new opportunities for research and development, technology transfer, and evaluation of next generation ITS technologies. Responses should take into account the critical role of advanced technologies in achieving transformative change in the areas of safety, mobility, environmental stewardship, and deployment policy. The RFI along with instructions for submittal can be found at http://www.regulations.gov under docket number RITA 2009-0001. Contact Kim Riddle: 202-366-5128.

  9. I am finding it slightly worrying that so many people have not heard of or are not familiar with the Active Traffic Management Scheme for instance hard shoulder running and variable speed limits.

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