Cruise Control: Description and Operation: Overview

Speed Control

OVERVIEW
There are two variants of speed control available, a standard system and an adaptive system. The standard system maintains a set speed selected by the driver until operation is suspended or cancelled by a further input from the driver and is controlled by the ECM (engine control module). The adaptive system includes the same functionality as the standard system, but also has the ability to:
- Reduce vehicle speed, to less than the set speed, in order to maintain a selected distance behind a slower moving vehicle
- Accelerate the vehicle back to the set speed, once the way ahead is clear, after reducing the set speed because of a slower moving vehicle
- Alert the driver when the vehicle comes within a given distance of a slower moving vehicle.

Speed Control
The standard speed control system has the following components:
- A SET + switch
- A - switch
- A RESUME switch
- A CANCEL switch
The speed control system also uses:
- The ECM (engine control module)
- The brake switch
- The APP (accelerator pedal position) sensor

Adaptive Speed Control
The adaptive speed control (also known as Adaptive Cruise Control (ACC)) system uses a forward looking radar sensor to scan the road ahead, looking for objects that are moving at a different rate to itself. When a target is identified the adaptive speed control system will monitor the time gap between the host and the target vehicles. When that gap falls below a set driver selected level, the speed control system will intervene, slowing the vehicle by backing off the throttle and/or applying the brakes, until the correct gap is attained. The driver can chose between four gap settings. The chosen setting is displayed in the instrument cluster.
The system will detect but not react to the following:
- Vehicles in the oncoming lane
- Stationary vehicles
- Pedestrians
- Vehicles not in the same lane.
Adaptive speed control is active when the vehicle is moving at a minimum speed of 20 mph (32 km/h) and a maximum speed of 112 mph (180 km/h). Adaptive speed control only functions when a set speed is entered in standard cruise control mode. The adaptive speed control system only intervenes with the set speed when it detects a target vehicle, and then only if the minimum time gap is breached.
It is important to note that the system is intended for use in limited driving situations, does not remove control and responsibility from the driver, and at all times can be quickly overridden. The adaptive speed control system is not a collision warning system and will not react to stationary objects. The system does not operate below a minimum speed of approximately 20 mph (32 km/h) since it is unsuitable for use in cities or congested traffic. The system is best suited to main roads/ highways with gradual bends.
The adaptive speed control system incorporates the following components in addition to those listed for standard speed control:
- An adaptive speed control radar sensor
- Steering wheel gap increase and decrease control switches
- The ABS (anti-lock brake system) control module.