Cruise Control and Safe Driving

Introduction to Cruise Control and Safe Driving

Advances in automotive engineering and technology provide us with both safety and comfort features in modern day vehicles. One such feature is our ability to put the vehicle in cruise control. With driver error blamed for so many cars crashes it is important that we are fully aware of how to use these features and devices correctly and safely.

There has been quite a bit of debate on the benefits and risks associated with driving a vehicle with cruise control. Engaging cruise control in any road situation that is less than optimal is ill-advised – but what are these conditions and how can we benefit from cruise control without compromising on safety?

There have been a few urban legends in the online media about vehicles with cruise control “aquaplaning”. There is however no inherent factor in the cruise control mechanism itself that could lead to a hydroplaning vehicle speeding up and flying through the air.

In this section, we would like to take a closer look at cruise control and find the truth about driving with cruise control. We need to know how cruise control functions, what the benefits and risks are and how and when to use or disengage speed control!

What is Cruise Control?

Cruise control can be used to automatically control the speed in your vehicle without keeping your foot on the accelerator. You are able to manage the speed of your car with your fingertips whilst still keeping control of the vehicle through the steering and braking. Cruise control was developed as a comfort and convenience system rather than a safety system

While cruise control systems and components may differ, each is equipped with similar functionality. The speed of the wheels is constantly being measured and fed into a cruise control system that regulates the engine's output. The cruise control systems are deactivated upon application of the brake pedal, which is usually deployed in emergency situations.

The basic features of most cruise control systems are:

The On/Off Switch

These buttons are used to engage and disengage your cruise control system. When you tap the “on” button, your car understands that you’re about to engage the system in order to cruise at a specific speed. The “off” button will disengage the cruise control. Turning off cruise control is as simple as applying the brake. Even a gentle tap of the brake pedal will shut cruise control off – requiring you to control the speed using your gas pedal again.

The Set/Accelerate Button

This button tells the vehicle to maintain the speed at which you are currently driving. As such, if you hit the “set” button your vehicle will maintain that speed once you remove your foot from the gas pedal. In most cruise control equipped cars, tapping the “accelerate” button will cause the vehicle to speed up by 1km/h.

Resume Button

Most cars’ cruise control systems will allow you to return to your previously programmed speed by pressing ‘Resume’.

Adaptive Cruise Control / Advanced Cruise Control

Advanced Cruise Control (ACC), also known as adaptive or intelligent cruise control, is an addition to conventional cruise control systems. It not only maintains the driver-set vehicle speed, but also adjusts the vehicle's speed to that of a preceding vehicle, and helps to maintain a pre-selected headway time to the vehicle ahead. Rather than maintaining speed in isolation, a vehicle with adaptive cruise control can actually react to the traffic around it.

Advanced cruise control uses a frontal radar/laser sensor to detect vehicles in front and subsequently adjusts the vehicle's speed and headway by controlling fuel flow or by slightly breaking. An adaptive cruise control-equipped vehicle can automatically slow down when the car ahead does; without driver intervention. It also means that if the driver changes lanes to an open one, the car automatically resumes speed. Most adaptive cruise control systems also allow the driver to set the following distance to the limits of the system's range, which is usually about 150m. While the majority of adaptive cruise control systems use radar, there are a few that use lidar or even cameras. Regardless of the sensor system involved, all systems provide essentially the same functionality.

Active braking carried out by ACC can usually reach up to maximally 30% of the vehicle's maximum deceleration. When a stronger deceleration is needed, the driver is warned by an auditory signal. Once the preceding, slower vehicle has moved out of the lane, the vehicle's speed will return to the driver-set cruise speed.

Benefits of Adaptive Cruise Control

A vehicle with adaptive cruise control can automatically slow down when the car ahead of it does, reducing the chance of rear-end collisions.
Adaptive cruise control also appears to improve traffic flow. According to the simulations, the presence of adaptive cruise control in as few as one-quarter of all vehicles on the road can lead to a marked improvement in traffic flow.

The only real drawback to adaptive cruise control is that it is more expensive than conventional cruise control. It is found more and more in the luxury car brands today!

Benefits of Cruise Control for the Driver

Cruise control may be intimidating for drivers who have never used it, as when they take their foot off the accelerator and the car doesn’t slow down, they feel like they are no longer in control of the car. Those who are familiar with how cruise control works may find the following benefits:

Cruise control was developed as a comfort and convenience system rather than a safety system.
It allows you to take long road trips with added comfort – driving long distances without putting a strain on your legs through having to hold your foot in a set position for extended periods to manually control the gas pedal and speed.
With cruise control activated, the driver can sit back, relax his right leg, and steer the vehicle.
For those of us who suffer from the lead-foot syndrome, cruise control ensures that you travel at a smooth and steady speed.
Most drivers are fairly inconsistent at maintaining a given speed, instead of creeping up and drifting down as you drive along a road as they manually adjustable relative to the speed limit and road conditions such as hills.
Accelerating and braking continuously will use considerably more fuel than maintaining a set speed.
Driving with cruise control will help to avoid subconsciously violating speed limits and incurring those unnecessary traffic fines on the open road.
It can help with fuel economy during long trips on flat, straight roads and highways.
The positives for road safety include a reduction of the mean driving speed, a reduction of the maximum speed, a reduction of speed differences, i.e. increased speed homogeneity and a reduction of the number of very short headway times.
As cruise control leads to a decrease in fuel consumption there should also be a decrease of harmful emissions.

What are the Risks of Using Cruise Control?

With increased comfort, there are however also risks that we need to be aware of! Driver error may lead to vehicle crashes if we use cruise control incorrectly and in the wrong driving conditions. Challenging road conditions may increase the risks for the driver using cruise control.

The driver should always be in full control of the movement of his vehicle and an error of judgement on his part cannot be merely blamed on the cruise control feature!

Risks can be summarized as follows:

Cruise control when deployed will attempt to keep the car at a constant speed set by the driver. If the vehicle speed has been set to a 100 km/h speed, the car will automatically enter a corner at 100 km/h. If this is an inappropriate speed for the corner the subsequent braking to reduce speed will, while cornering, affect the balance of the vehicle which may, in turn, induce instability in the vehicle.
This will affect the vehicle handling and if not correctly compensated for by the driver, can in the worst case result in a loss of control of the vehicle.
Cruise control may lead to increased lane position variability, delayed braking, and crashing into a stationary queue more frequently.
Wet roads significantly affect the grip of the tyre and this, in turn, can make corrective actions by the driver much more difficult to judge.
A driver should remain alert while driving - Fatigue and a false sense of security can lead to a lack of attention and an accident.

Cruise control should NEVER be used by a driver who is feeling tired or jaded.
The lack of need to maintain constant pedal pressure can increase the risk of vehicle accidents caused by highway hypnosis
Cruise control can also take your mind off the road (frequently, drivers keep one hand on the wheel while in cruise control, and that’s their only contact with the vehicle).
With less to concentrate on it’s easier to daydream and disconnect from driving safely, which always requires concentration.
Another risk is that a driver may not be able to respond as swiftly and effectively to an emergency situation.
With cruise control, it takes the driver’s foot off the gas pedal and the brake. The driver usually keeps his foot on the floor nearby. If you have to stop suddenly, to avoid a hazard on the road, it will take a few extra mille-seconds to find the brake pedal, and this time makes a lot of difference in what happens next.
Driving over "rolling" terrain, with gentle up and down portions, can usually be done more economically (using less fuel) by a skilled driver viewing the approaching terrain, by maintaining a relatively constant throttle position and allowing the vehicle to accelerate on the downgrades and decelerate on upgrades, while reducing power when cresting a rise and adding a bit before an upgrade is reached.
If Advanced Cruise Control is used in busy traffic, and on rural and urban roads other than main roads, there is a potential reduction of the ACC detection capacity.
Accidents, merge lanes, exit congestion—all are possible highway hazards that are hard to anticipate, and harder to avoid when you’re on cruise control

When not to use Cruise Control

It is important to read the owner’s manual as a guide to when cruise control should be avoided. Cruise control is designed for ideal road conditions. Some manuals suggest cruise control should not be used in "heavy traffic driving, city driving, winding, slippery or unsealed roads.

We would like to advise that cruise control by avoided in the following circumstances:

Never use cruise control where you cannot drive at a steady speed.
Don’t use your cruise control when the road is wet and slippery due to heavy rain, hail, snow, ice, or in other challenging road, weather and environmental conditions.
High-risk road conditions will include having to drive where visibility is poor such as in fog and mist or areas of veld and forest fires.
Do not use cruise control when driving in high traffic, and on rough, narrow, hilly or excessively bendy roads

If your wheels begin to skid and you don’t step on the brake to stop, the continued acceleration can cause you to overdrive the road conditions and lose wheel traction and control of the vehicle.
Using cruise control in traffic and on city streets with lights and stop signs can be tedious, frustrating, and unsafe. In these situations, you need to reset your cruise control each time you brake and it is unlikely you would be driving at the minimum speeds needed for cruise control.
It is best to manually control your vehicle in traffic and city streets and leave cruise control for long journeys on dry, straight, and wide-open highways.
Advanced cruise control should not be used on rural roads with curves and intersections, or on urban roads, because of difficulties in detecting small silhouettes and vehicles out of the line of vision on these road types.

Advice on safely using Cruise Control

As a safe starting point, we would like to advise reading your vehicle owner’s manual on how to operate your vehicle’s cruise control feature – Pay attention to the manufacturer’s warnings about cruise control use.
It remains the duty of the driver to assess the conditions of the road and adjust vehicle speed to a safe speed suitable for the road and current driving conditions.
The safest way to operate a vehicle is to ensure that under all driving conditions you can control the vehicle (brake, corner and accelerate) in a safe manner.
During cruise control, your foot may take a rest from the accelerator, but keep both feet flat on the driver’s side floor and ready for braking or manoeuvring if you need to suddenly slow or emergency stop.
Don’t lounge, curl your foot up underneath you, or put it up on the dashboard, windowsill, etc. while you drive.
Even though you may not have to control your accelerator you still need to control the brake pedal at all times.
The brake pedal will disable cruise control, so be aware if the brake pedal is accidentally hit or pressed while driving.

The Future

As with other vehicle components we can expect to see continued improvements and advances in features and technology. Communication between vehicles and between vehicle and roadside is considered the technology that will make a whole new generation of vehicle control systems possible.

Cooperative Advanced Cruise Control with communication between a series of successive ACC-equipped vehicles in the same lane and/or communication with roadside systems will lead to vehicles exchanging information on their position, speed and deceleration. This may benefit road safety as the ACC system can optimize its speed support and drivers can get early warnings of braking or of slow vehicles ahead.

We will continue to assist road users with a better understanding of our vehicles and how we can make informed decisions to improve the safety for all on our roads!!

Recognition to info from

The Institute for Road Safety Research
Advanced Drivers of America

Also view:

Advanced driving and road safety

Following distances and safe driving

Driver fatigue and road safety