Sizing up how tight a curve is lets you pick a safe speed before you enter it, and setting your lane position ahead of time lets you follow the curve smoothly. Doing both early helps the tires keep their grip and keeps the car from drifting into another lane.
Big speed differences between vehicles lead to more passing, sudden braking and lane changes, which raise the risk of a crash. Moving at about the same speed as surrounding traffic, without going over the posted limit, keeps those conflicts to a minimum.
Vehicles moving far below the speed of everyone else disrupt the flow and invite rear-end crashes and risky passing, so some highways set a minimum speed to keep traffic moving evenly.
When speeds differ, conflicts multiply: a faster driver keeps overtaking and weaving around others, while a slower one forces the drivers behind to brake hard or swerve and is more likely to be rear-ended. Keeping pace with traffic, within the legal limit, is safest.
The speed law forbids driving faster than is safe for the conditions, even below the posted limit. Rain, fog, heavy traffic or a sharp curve can make the safe speed much lower than the sign shows, and you can be ticketed for unsafe speed without going over the limit.
The posted limit is the most you may drive in good conditions, but the speed that is actually safe changes with weather, traffic and the road surface. On an icy or foggy highway, a safe speed can be far below the legal limit.
The Basic Speed Law means your speed must always suit the conditions, including weather, traffic and visibility, no matter what number is posted. Keeping up with faster cars, or driving at the limit in heavy rain or fog, can still break this law.
Each pass on a two-lane road puts you in the oncoming lane for several seconds, so passing again and again keeps exposing you to a head-on collision. The time saved is small, and it is safer to keep pace with the flow of traffic within the speed limit.
Going downhill, gravity keeps pushing the car faster, and leaning on the brakes alone can overheat them until they stop working well. A lower gear lets the engine help hold the car back, so only light, careful braking is needed.
This white rectangle reading SPEED LIMIT 55 is a regulatory sign that sets the highest legal speed on the road, 55 mph. Regulatory signs state rules drivers must obey, such as speed, turning, lane use and parking.
Before you reach a curve, decide whether your speed will let you take it safely, and do any slowing while the car is still going straight. Braking in the middle of a curve can cause the tires to lose grip, and warning signs before curves often show a safe advisory speed.
Matching the speed of the traffic around you, within the limit, is usually safest, so 35 mph is the best choice here even though the sign allows 65 mph. Going faster would mean constant braking and weaving, while going noticeably slower than the flow invites rear-end collisions.
Slow down when traffic is heavy or the weather is bad, but driving well below the normal flow gets in other drivers' way and can earn you a ticket. Keeping pace with surrounding traffic, within the speed limit, is usually safest.
Posted limits are meant for good conditions. Rain, fog, snow, darkness, heavy traffic, road work or anything else that makes driving harder calls for a speed below the number on the sign.
Do your braking on the straight stretch before the curve rather than inside it, because braking in the curve can make the vehicle skid or lose traction. With your speed already reduced, you can drive through with control and accelerate gently on the way out.
Every question in this set has its own page with the correct answer and an explanation.
