Hazard Perception Handbook - Keeping Space From Other Vehicles

Crash avoidance space

Hazards could be other vehicles changing lanes or braking suddenly to avoid a pedestrian who walks onto the road. To stay safe, you need to maintain a crash avoidance space around your car by adjusting your speed or position on the road.

Maintaining a crash avoidance space to the front

Maintaining a crash avoidance space to the front gives you more time to spot and respond to hazards. Running into the back of another vehicle is the most common (29%) type of crash for provisional, drivers making this the most important part of the buffer for provisional drivers. To maintain adequate space to the front you need to:

Control your speed to suit the road and traffic conditions
Keep a safe distance between your car and the vehicle in front

Controlling your speed

Speed limits, speeding and crashing

Speed limits (mainly between 40km/h and 110km/h) are the maximum permitted speed even though good drivers adjust to slower speeds based on the conditions. Speeding is not OK and is a factor in 40% of fatal crashes.

Travel time surveys show that speeding makes little difference to your travel time in built-up areas. Speeding does increase the risk of a speeding fine or crash and costs you more in fuel consumption.

The problems with speed

Speeding reduces the time to detect and react to hazards. Increased speed and wet weather increases distance required to stop. It takes 0.75 seconds to see a hazard and decide on a response and another 0.75 seconds to act (move foot from accelerator to brake). So 1.5 seconds are gone before you begin to brake.

Speeding and crash severity

More than 2,000 pedestrians are injured or killed each year with provisional drivers over-represented in these accidents. Risk of death increases with speed. At 60km/h hitting a pedestrian will likely kill them. At 50km/h they are more likely to be injured than killed – which is why 50km/h is the common local speed limit in NSW.

Speed and single vehicle crashes

Speed is a common cause of provisional driver single vehicle crashes. Driving too fast for conditions reduces the time to detect and respond to hazards. Speed-related crashes can be avoided if you give yourself time and space to scan for, detect and react to hazards. Some advice:

Don’t speed
Slow down before curves and bends (not during)
Look for traffic warning signs and slow down when required
Slow to warning sign speed (or slower)
In bad conditions, slow to speed that will allow you to stop for an unexpected hazard

Warning signs won’t help if you’re going to fast to see or react to them. Controlling your speed is your responsibility.

Key points summary

Maintain a crash avoidance space around you vehicle and adjust your speed to best suit the conditions.
Slow down and take your foot off the accelerator where hazards are likely (e.g. pedestrians areas)

Keeping a safe following distance

Initial speed (km/h)	60	90	Roughly twice the distance on sealed, dry road
Approx. stopping distance (m)	55	110	Roughly twice the distance on sealed, dry road

As speed increases, so should the gap between you and the vehicle in front as the stopping distance required increases. To ensure this use the ‘3-second gap’.

The three second gap

Pick a stationary object the car in front passes (e.g. traffic sign) and count to three. You should pass the same object as you count three or after. If you don’t reach three, slow down until you do. These techniques automatically adjust for your speed (increasing the gap as you go faster). You should use the 4-second rule to increase the gap (and safety) in poor conditions including rain, fog, icy roads or night driving.

Although these might seem like large gaps, remember that rear-end collisions are the most common crash types, so the gaps are necessary to avoid crashes.

Key points summary

The faster you drive, the more stopping distance required
Use the 3-second gap in good conditions and 4-second gap in poor conditions
In heavy traffic other drivers will likely move into your 3-second gap. The gap ensures your safety which is more important than one place in traffic, so maintain the 3 seconds regardless

Keeping a safe distance to the side

A space cushion allows a safe distance should you need to brake or change direction, potentially allowing you to avoid a collision.

You should keep at least 1 metre between your vehicle and other moving or stationary vehicles (in case someone opens their door unexpectedly). This also protects vulnerable road users, reducing your chances of hitting them.

Avoid travelling next to other vehicles

Try to avoid having a vehicle on either side of you on multi-lane roads as your vision is impeded and your only option is to brake hard for a hazard in front of you. A better option is trying to keep space in the next lane/s so you can also move around a hazard. This might be difficult in heavy traffic, though this usually means you’ll be moving slowly and there’s less risk generally.

Key points summary

Keep a 1 metre space cushion either side of car
Avoid travelling with vehicles either side of you
Give vulnerable road users plenty of space

Keeping a safe distance to the rear

Managing the space behind you is difficult as it mainly relies on the driver behind you. If they’re too close, slow down to give yourself extra space ahead of you. This will give you more time to slow down for a hazard and will reduce the risk they will run into you.