Speed and stopping distance — North Carolina Permit Test

The speed at which you drive determines the distance required to stop; stopping distance also depends on reaction time, and both grow with speed.

Doubling your speed does more than double your stopping distance. The car covers ground while you are still deciding to brake.

Stopping distances are longer at higher speeds because a vehicle travels farther during the driver’s reaction time, and it takes more braking distance to come to a full stop.

Even with ideal conditions, a vehicle traveling 55 miles per hour requires approximately 211 feet to stop completely.

That is most of a football field, on a dry road with good brakes. Rain and worn tires make it longer still.

Even with ideal conditions, if you are traveling 55 miles per hour your vehicle requires approximately 211 feet to stop completely.

Driving well below the posted limit can also be dangerous: a slow driver forces others to creep along or take risks passing, and is more likely to be in a crash than a driver at normal speed.

A slow car on a fast road is an obstacle. The crashes happen behind it, when faster drivers run up on it or try to get around.

Studies show that the vehicle moving at a speed considerably below the posted limit is much more likely to cause or be involved in a crash than the vehicle moving at a normal speed.

If you must drive slower, observe the posted minimum speed limit, and if traffic is collecting behind you, pull over to the side of the road, stop and let the vehicles pass.

A line of cars behind you is a line of drivers losing patience. Letting them by is safer than making them pass.

If traffic is collecting behind you, it is wise to pull over to the side of the road, stop and allow the vehicles to pass.

Never drive faster than the posted speed limit, or at a speed that is unreasonable or unwise for the conditions, and the faster you go the farther ahead you must be able to see.

The posted number is a ceiling for a good day. In rain, fog or traffic the safe speed is lower, and the law expects you to find it.

Never drive faster than the posted speed limit or at a speed that is unreasonable or unwise given the existing conditions.

Unless otherwise posted, the speed limit is 35 mph in cities and towns.

Town streets have driveways, parked cars and people. The limit is low because there is so much to stop for.

Unless otherwise posted, the speed limit is 35 mph in cities and towns.

The maximum speed limits are 35 mph in cities and towns, 45 for school buses, 55 for school activity buses, 55 outside cities and towns, and 70 on interstates.

Outside town the road opens up but it is still a two-way road with driveways and crossings. The limit is 55, not interstate speed.

Maximum Speed Limits In cities and towns 35 For school buses 45 For school activity buses 55 Outside cities and towns 55 For interstates 70

The maximum speed limit on North Carolina interstates is 70 mph.

Interstates have no crossings, no sharp curves and no oncoming lane. That is why they carry the highest limit in the state.

Maximum Speed Limits In cities and towns 35 For school buses 45 For school activity buses 55 Outside cities and towns 55 For interstates 70

The maximum speed limit for a school activity bus is 55 mph, ten more than a regular school bus.

An activity bus runs on highways between towns, so it gets the open-road limit. The school bus on its route does not.

Maximum Speed Limits In cities and towns 35 For school buses 45 For school activity buses 55 Outside cities and towns 55 For interstates 70

Why are stopping distances longer at higher speeds?

More ground is covered reacting, and braking takes longer. Doubling your speed does more than double your stopping distance. The car covers ground while you are still deciding to brake. North Carolina Driver Handbook, p.52: “Stopping distances are longer at higher speeds because a vehicle travels farther during the driver’s reaction time, and it takes more braking distance to come to a full stop.”