Stopping distances: speed and braking
The simple truth about speeding is: the faster you go, the longer it takes to stop and, if you crash, the harder the impact. Even small increases in speed could have severe consequences. If a pedestrian steps out into the path of an oncoming vehicle which is speeding the difference could be a matter of life or death.
The stopping distances on the infograph are calculated based on the following assumptions:
- In an emergency the average driver takes approximately 1.5 seconds to react
- A modern vehicle with good brakes and tyres, after braking, is capable of stopping at approximately 7 m/s2.
- A dry road that is sealed and level enables good friction between the tyres and the road to help stop the vehicle sooner. Scientifically, it has a coefficient of friction of approximately 1.
- A wet road that is sealed and level has less friction between the tyres and the road which increases the stopping distance of a vehicle. Scientifically, the coefficient of friction of approximately 0.7.
The stopping distances in the graph are generic and may be influenced by a number of driver, vehicle and environmental factors:
| Driver factors | Vehicle factors | Environmental factors |
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Stopping distances on a dry road
The following table shows the distance needed to stop on a dry road in an average family car.
| Speed | Reaction distance | Braking distance | Total stopping distance |
|---|---|---|---|
| 40km/h | 17m | 9m | 26m |
| 50km/h | 21m | 14m | 35m |
| 60km/h | 25m | 20m | 45m |
| 70km/h | 29m | 27m | 56m |
| 80km/h | 33m | 36m | 69m |
| 90km/h | 38m | 45m | 83m |
| 100km/h | 42m | 56m | 98m |
| 110km/h | 46m | 67m | 113m |
Stopping distances on a wet road
The following table shows the distance needed to stop on a wet road in an average family car.
| Speed | Reaction distance | Braking distance | Total stopping distance |
|---|---|---|---|
| 40km/h | 17m | 13m | 30m |
| 50km/h | 21m | 20m | 41m |
| 60km/h | 25m | 29m | 54m |
| 70km/h | 29m | 40m | 69m |
| 80km/h | 33m | 52m | 85m |
| 90km/h | 38m | 65m | 103m |
| 100km/h | 42m | 80m | 122m |
| 110km/h | 46m | 97m | 143m |
Driving on unsealed roads
Not all roads are sealed with bitumen. Driving on unsealed roads can be more difficult than driving on bitumen.
Unsealed road surfaces include gravel, sand or dirt. These surfaces can make your tyres lose traction with the road. You should decrease your speed when travelling on these roads and increase the distance between you and the vehicle in front.
Weather can also affect driving conditions on unsealed roads. Some examples of how weather affects your driving include:
- dry weather can create dusty conditions and limit your visibility
- wet weather can make roads muddy, slippery and boggy.
Driving in dusty conditions
Dust can be caused from strong winds and driving on unsealed roads. These conditions can reduce your visibility on the road.
If you are driving through dusty conditions:
- pull over, stop and wait for the dust to settle
- turn on your lights so other vehicles can see you.
Driving in sandy conditions
Driving on sand is very different to driving on a sealed road surface. Sand over the road can make your vehicle lose traction when driving. You should avoid sharp turns, drive slowly and keep up your momentum to avoid spinning your wheels.
Sand locations such as beaches are not suitable for vehicles other than 4WDs. When driving a 4WD on sand, make sure you:
- engage 4WD locking hubs and use low gears
- deflate your tyre pressure for better traction—carry an air pump and re-inflate when you drive on hard surfaces
- bring a jack and shovel in case you get stuck or need to change a tyre
- pack your vehicle correctly with the heaviest items stored low—don’t over-pack your roof racks as this can make the vehicle overturn
- make sure you have a first-aid kit and call 000 in an emergency.
Beach driving
You can drive 4WDs on many beaches and inland tracks throughout Queensland—first check if you need a vehicle permit. There are also extra restrictions for driving a 4WD on Fraser Island.
Normal road rules apply with beach traffic being 2-way—so remember to keep left, obey the signed speed, wear your seatbelt and never sit outside the moving vehicle.
When driving on the beach:
- travel at low tide or within 2 hours either side of the low tide
- avoid salt water—stay on the harder sand between the waterline and the high tide mark to get the firmest driving surface
- avoid rocks, pools, and washouts
- watch out for pedestrians, wildlife, other vehicles and landing aircraft.
Driving on country and remote roads
When driving in the country or along remotely located roads:
- reduce your speed before nearing the edge of the road—the edge may drop off or have loose stones
- keep 1 wheel on the bitumen due to the unstable nature of road edges.
- if you’re driving towards the west, the afternoon sun can affect your vision from 4pm
- keep an eye out for livestock and wildlife on or at the side of the road, especially at night. Slow down and beep your horn if you see animals at the edge of the road about to cross.
Driving near heavy vehicles
Heavy vehicles are heavy and long. They take longer to stop and accelerate than smaller vehicles and require more room when turning. If you are driving behind a heavy vehicle, keep a 2-second distance between you and the heavy vehicle—double this distance in bad driving conditions.
Tips when driving near heavy vehicles include:
- do not cut in front of heavy vehicles because you reduce the driver’s breaking distance
- do not speed up when a heavy vehicle overtakes you.
- if you are behind a heavy vehicle and you cannot see its side mirrors then assume that the heavy, vehicle driver cannot see you
- do not tailgate a heavy vehicle. You cannot see what is ahead of it and you won’t be able to react in time
- never overtake a turning vehicle that has a DO NOT OVERTAKE TURNING VEHICLE sign displayed—it is dangerous and you can get a fine.
Overtaking a road train
Road trains are large truck and trailer combinations more than 19m long. You should only overtake when it is safe and road markings indicate you can.
Before you overtake:
- allow enough time to overtake
- stay back at the recommended following distance (2 second distance) without crossing the centre line when preparing to overtake
- look out for soft shoulders, guide posts and wildlife as you overtake
- when it’s safe to overtake, indicate, accelerate and overtake quickly without exceeding the speed limit. Changing down a gear may give you enough engine power to get past
- maintain your speed so the road train does not have to brake after you overtake
- Do not overtake a turning vehicle at an intersection, unless it is safe to do so.
