Car speed synchronization systems

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Car speed synchronization systems utilize sensors mounted on the vehicle to automatically match the speed of surrounding traffic. The functionality of these systems vary from Advanced Emergency Braking Systems/Collision Avoidance Systems to prevent a crash, Intelligent Speed Adaptation (ISA), and even commercially available after market kits to tie vehicle speed to limits in various jurisdictions [1]. Factory installed in and increasing number of vehicles, these systems -also referred to as autonomous cruise control, radar cruise control, adaptive cruise control, and cooperative adaptive cruise control (CACC)- can increase efficiency and roadway capacity by allowing vehicles to coordinate their movements, shorten distances between cars, and avoid unnecessary acceleration and breaking. This saves fuel, reduces emissions, and prevents the cascading delays and crashes that are common during congested conditions [2]. These systems may provide substantial benefits even if used in only one car in five [3].

Though there are benefits for both private and commercial users of car speed synchronization systems, governments may wish to promote integration of the technology into vehicles and, potentially, require the sunsetting of non-compatible vehicles. Even when installed in vehicles, changing driver behavior may require incentives and ad campaigns to publicize the efficiency and safety of the systems, especially during the congested conditions where, unlike traditional cruise control, speed synchronization systems are of most use.



A state with substantial automotive congestion wants to increase capacity on major thoroughfares with minimal disruption of traffic and minimal cost to the state. They decide to create a program to increase the efficiency of traffic by using programmable highway signage and other low-cost media strategies to promote the use of the speed synchronization/CACC systems that an increasing number of drivers already have installed in their vehicles. The program create a new norm that drivers in the inner lanes of multi-lane roadways are expected to utilize the speed synchronization system in their vehicle and makes drivers aware of the potential benefits to them in their daily travel. In later phases, separate, dedicated lanes where use of these systems is required could be paired with the added incentive of higher speed limits in these lanes. The educational program and dedicated lanes would result in voluntary behavioral changes among a subset of drivers and create significant capacity and safety increases on the region's most congested roadways.

Presently, jurisdictions worldwide are in different stages of drafting legislating to deal this fast developing technology. In the US few states- currently only California, Nevada, and the District of Columbia- have explicit policies for licensing and regulating vehicles equipped with advanced speed synchronization and other automated and autonomous systems; the resulting ambiguity forces companies to travel to other jurisdictions in order to conduct the exhaustive on-road testing these systems require [4]. State governments such as Massachusetts view this lack of regulation as providing an opportunity to boost their economies by encouraging companies to relocate to their state for more streamlined development procedures [5].


Tradeoffs of implementing this policy may include:

  1. Reductions in environmental impacts may decrease over time due to induced demand and an increase in total vehicle miles traveled.
  2. Increased capacity on major roadways may increase congestion on feeder roads.
  3. Improvements in travel time may decrease over time due to additional capacity being used due to induced demand.
  4. Increased capacity may increase the rate of wear on roadways and necessitate more maintenance.
  5. Lower fuel costs and improved experience may make drivers feel less pressure to make other changes which could reduce environmental impacts of travel such as using public transit or taking other steps to increase their fuel efficiency.
  6. Increased susceptibility to cyber threats when vehicles are networked together [6]
  7. Any system failure would pose increased danger due to closer travel distances and decreased driver attention.
Compatibility Assessment

If answered yes, the following questions indicate superior conditions under which the policy is more likely to be appropriate:

  1. Is there significant congestion on roads within the jurisdiction?
  2. Is a significant share of traffic congestion primarily due to vehicles which possess speed synchronization technology (newer vehicles)?
  3. Does the roadway have programmable signage or are funds available to create new (static or programmable) signage for the initiative?
  4. Is the promotion of car speed synchronization systems likely to be more cost effective than alternative environmental impact and traffic mitigation measures such as traffic signal synchronization and fuel efficiency standards?
  5. Does the level of government/municipality have the administrative capacity and legal authority to implement such a program?


The following questions should be considered when determining how to implement this policy:

  1. What are the goals of this implementation?
    1. Even low levels of utilization can result in marked improvements in efficiency and safety, but more ambitious goals may require much higher utilization rates or more broad geographic implementation; authorities should be clear internally and with the public what is possible from the chosen strategy.
  2. Would the overall efficiency of the region's transportation network increase?
    1. There should be other measures in place to maintain modal share of other transportation methods.
    2. There must be sufficient capacity on feeder roads to support increased capacity on the targeted thoroughfare.
  3. Does this support other planning goals?
    1. Improvements in capacity on limited-access routes (urban freeways) have historically been shown to support urban sprawl (decreasing densities in a metropolitan area and urban centers stagnate.
    2. Improving automotive transportation may reduce public interest in alternative transportation investments which may be more in keeping with long-term sustainability.
  4. What additional interventions, if any, will be implemented in order to increase the effectiveness of the campaign?
    1. If demand is expected to increase more than can be accommodated by increased capacity due to speed synchronization, further policy interventions or capital investments will be needed and should be planned for.
    2. On roadways with complex traffic patterns and frequent needs for lane changes, there may be less opportunity for speed synchronization to improve efficiency.
    3. If incentives or mandates are aggressive enough to cause to consumers and businesses to replace a vehicle before they normally would for economic reasons, they may postpone investing in subsequent vehicles and this should be accounted for in any estimates of environmental benefits.
    4. Participation incentivized by providing tax rebates, access to HOV lanes, or other benefits that would be both compatible with the program goals and desirable to participants.
    5. Adoption of speed synchronization technology could be mandated by requiring that all vehicles have speed synchronization systems by a certain date whether through retrofitting or replacing older vehicles with newer vehicles on which such technology is standard.






  • Cooperative Adaptive Cruise Control: Human Factors Analysis Jones, Stephen. (2013) Office of Safety Research and Development Federal Highway Administration. Report No.: FHWA-HRT-13-045A. Report describing the human interactions necessary in Coordinated Adaptive Cruise Control and potential problems to address.
  5. Graham, Jordan (2016). Massachusetts to Begin Developing Policies for Testing Driverless Cars, Boston Herald. Available at: [1].
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