Road Network Operations
& Intelligent Transport Systems
A guide for practitioners!

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Vehicle Control

Over the last few years automotive manufacturers have been introducing sophisticated vehicle control technologies to improve safety, fuel efficiency and comfort level of drivers, amongst other things. These new technologies are sometimes called Advanced Driver Assistance Systems (ADAS). These systems use sensor technology, including automotive radar, that has been developed specifically for use in motor vehicles (See Warning and Control). They have a positive effect on safety and traffic management by helping drivers to maintain a safe speed and distance, keep within the running lane and avoid unsafe overtaking manoeuvres. Benefits can be further magnified if individual vehicles communicate continuously with each other or with the road infrastructure – so-called ‘connected’ vehicles (See Connected Vehicles).

Longitudinal Vehicle Control

Examples of longitudinal vehicle control are Adaptive Cruise Control (ACC) and Co-operative Adaptive Cruise Control (CACC). ACC is designed so that a car automatically maintains a safe distance from the vehicle ahead in terms of distance or time headway, as programmed by the driver. The driver specifies the maximum speed (as with normal cruise control) and the follow distance. An on-board radar sensor locks onto the vehicle ahead and the vehicle control system maintains the specified distance. ACC is often accompanied with a forward collision warning system that alerts the driver in case of an obstruction hazard ahead. It may even start to apply the brakes if the driver fails to do so.

Research is taking place that combines ACC with inter-communications between vehicles.. With communications added, ACC becomes Co-operative Adaptive Cruise Control (CACC). Communications allow the front vehicle’s rate of acceleration or deceleration to be communicated in real-time to the vehicle following (several times per second). The real advantage of CACC is to reduce delay in the response of the vehicle behind.

Lateral Vehicle Control

Some high-end new cars on the market now include lane departure warning systems and lane-keeping support systems. These keep track of the vehicle’s position relative to the running lane. They use a suite of sensors such as video sensors mounted behind the windshield, laser sensors on the front of the vehicle, and/or infrared sensors under the vehicle. Warning systems only sound if the vehicle starts to deviate from the lane, whereas lane-keeping support systems may take remedial action to return the vehicle to a safe position within the lane.

Autonomous or self-driving vehicles

By combining technologies, the next evolution in vehicle control systems is autonomous or self-driving vehicles.

The US National Highway Traffic Safety Administration (NHTSA) has defined five levels of automation to describe systems with varying degrees of autonomyin the following way:

  • Level 0: no automation – the driver alone is responsible for vehicle control in terms of braking, steering, clutch and accelerator
  • Level 1: is function-specific automation – where one or more specific control functions of the vehicle are controlled automatically (such as electronic stability control or pre-charged brakes)
  • Level 2: is automation involving at least two primary control functions (such as ACC with lane-keeping) – to release the driver from having to control such functions
  • Level 3: involves periods where the vehicle may truly self-drive (the driver relinquishes all control to the vehicle). This level assumes that the driver is still available to regain control under certain traffic or environmental conditions (such as snow or ice). A sufficiently comfortable transition time needs to be available to the driver for safe hands-off.
  • Level 4: is a fully autonomous vehicle capable of performing all safety-critical driving functions and of monitoring the traffic and roadway conditions for the whole trip. A driver need not be physically present inside the vehicle.

The Google car is an example of what is in development and on trial in California. youtube (See Video)

Reference sources

World Road Association Technical Committee on Road Network Operations (2016). Cooperative Vehicle Highway Systems. Report 2016R08 World Road Association (PIARC) Paris. ISBN 978-2-84060-386-3. Available from the Internet site of the World Road Association.