You should always keep your speed below the maximum speed limit for the road you are driving on. Although you are not legally obliged to drive at the maximum speed limit, if it is safe to do, you should try and drive at a speed that at least approaches it. For instance, in a 40mph zone, your speed should be between 35 and 40mph.
Driving too slowly can be as dangerous as driving too fast. The driver who toddles along a 60mph road at 40mph causes tailbacks and frustration. This can lead to dangerous overtaking manoeuvres and other road safety issues.
Speed in itself is not that dangerous, but inappropriate speed is. Always take into account the weather and road conditions. Driving at 60mph, even though you are legally entitled to do so when there is ice on the road is dangerous and inappropriate, as is driving at 40mph on a dual carriageway when the weather is fine.
The general speed limit rules for cars are:
These speed limits apply at all times, whether during the rush hour or the dead of night and are overridden only if a road sign indicates a different speed limit, for instance, it is not uncommon to have a speed limit of 40mph on a road that has street lighting.
Minimum Speed Limits
You won't often encounter a minimum speed limit however they are sometimes put in place where it is important to keep traffic moving smoothly.
The table below shows the national speed limits for different vehicles on different types of road.
The Correct Gears You Should Use
Different gears are used to reach and maintain different speeds. The general guideline is as follows:
The distance, over which you can bring a car to a stop, the stopping distance, depends on four factors.
The following diagram shows overall stopping distances at a variety of speeds when the road surface is dry. If the road were wet the stopping distance would be twice the distance, on icy roads the stopping distance would be ten times as great.