Allow one second for every 10 feet of length, or 6 seconds for a 60-foot vehicle, and add a second when traveling faster than 40 mph. At 50 mph the total is 7 seconds.
Counting seconds from a fixed reference point turns following distance into a real measurement instead of a guess. Compare the count with the minimum for your vehicle's length and speed, and allow more time in bad weather or heavy traffic.
Because the suspension squats under weight, a truck rides lower when loaded and higher when empty, so an overpass you cleared with a load may be too low on the trip back. Posted heights can also be wrong after repaving or packed snow, so never assume they are accurate.
When there are two left-turn lanes, a long vehicle should turn from the right-hand one. Starting in the inside lane may force you to swing right during the turn, into the path of vehicles turning beside you, and switching lanes at the last moment creates the same conflict.
Driving next to another vehicle is risky: its driver may change lanes into you, and you may be boxed in when you need to move over. Look for a place in traffic where no one is beside you, and keep your vehicle centered in its lane.
A bus picks up speed slowly, so it needs a long opening to merge without forcing others to brake. Judge the space your bus requires and pull out only when traffic leaves a gap that size.
Because of off-tracking, the rear wheels of a long vehicle follow a tighter path than the front ones, so you need to reach the center of the intersection before you turn left. Turning too soon can bring the left side of the vehicle into other traffic, and on a two-way street the left lane belongs to oncoming drivers.
Start the turn with the rear of the vehicle near the curb, and swing wide only as you complete it, so nobody can squeeze by on your right. If you swing left first, the driver behind may assume you are making a left turn and try to pass on the right, and driving over the curb can hit pedestrians or signs and poles on the sidewalk.
When traveling slower than 40 mph, leave at least one second of following time for each 10 feet your vehicle measures. For example, a 40-foot truck needs a minimum of 4 seconds, and a 60-foot rig needs 6.
Choose a landmark such as a sign or pole, begin counting as the vehicle in front passes it, and stop counting when you get there yourself; that number of seconds is your following distance. Timing it with a handheld phone while driving is a dangerous distraction.
Each new layer of pavement raises the road surface, so the real space under a bridge can end up smaller than the posted height; packed snow can have the same effect. If you are not sure your vehicle will fit, go slowly or take another route.
A vehicle running next to yours could swerve into your path with no warning, and it also boxes you in if you need to change lanes in a hurry. Keep your rig centered in its lane, and remember that strong winds make lane keeping harder, not easier.
The rule calls for one second for each 10 feet of vehicle length, plus one more second at speeds above 40 mph. A 50-foot rig at 50 mph therefore needs 5 + 1 = 6 seconds, and even more when the road or weather is poor.
Traveling beside another vehicle for long is risky: it might wander into your lane and strike the bus, and it boxes you in if you need to change lanes. When you can, stay ahead of or behind other traffic.
You allow one second per 10 feet of vehicle length, and add a second more when going faster than 40 mph. For a 30-foot vehicle that is 3 seconds, and since you are at 55 mph there is 1 extra, giving 4 seconds in total.
Tip Above 40 mph, divide the vehicle's length in feet by 10 and add one second, so 30 feet works out to 3 plus 1, or 4 seconds.
A long vehicle should move forward into the intersection and swing wide only while finishing the right turn, keeping its rear near the curb so nobody can slip past on the right. If you swing out to the left first, the driver behind you may assume you are turning left and attempt to overtake on your right.
The rear wheels of a long vehicle follow a shorter path than the front wheels, so a turn started too early can make the back end cut across the corner and strike vehicles or objects on the left. Pull forward to about the middle of the intersection before you begin turning.
A vehicle that cannot turn right without swinging wide should go straight ahead into the intersection and swing wide only as it completes the turn, keeping its rear close to the curb so no one can slip by on the right. Swinging left before starting the turn is the mistake, because it leaves room for another driver to pass you on the right.
A heavy vehicle accelerates slowly and needs more room to get moving, so wait for a much larger gap than a car would need. Never block a lane while waiting, and do not assume others will slow down or move over just because your vehicle is big.
The basic rule of one second for each 10 feet of vehicle length, plus one extra second above 40 mph, is meant for good conditions. On a slippery road you need much more room than that, because it takes far more distance to stop.
A bus needs plenty of room to get up to speed and merge, so judge that space and leave the stop only when traffic offers a gap big enough. Do not count on other drivers to make way for you.
To join an expressway safely, scan the traffic already on it, signal so others know your plan, and ease into the proper lane without sudden moves. Stopping on the ramp or ignoring the speed of traffic makes merging much harder.
Ice, snow, rain and other slick surfaces reduce traction, so stopping distance grows sharply and you should leave a much bigger gap than usual. Crashes come from too little space, not too much, and heavier vehicles generally need more room to stop than small ones.
Following distance starts at one second per 10 feet of vehicle length, which gives 3 seconds for a 30-foot bus. That is the minimum below 40 mph; above 40 mph, one more second is added.
More room ahead lets you slow down gradually if traffic stops, which gives the tailgater time to react and makes a rear-end crash less likely. Avoid tricks like flashing your brake lights, and do not wave other drivers past.
Pick a fixed point such as a sign or an overpass; when the rear of the vehicle ahead passes it, count the seconds until your front end reaches it. A large vehicle should keep at least one second for every 10 feet of its length, plus one more second at speeds above 40 mph.
The guideline is one second for each 10 feet of vehicle length, so a 40-foot bus needs 4 seconds. Above 40 mph you add one more second, which brings the total to 5.
Base following distance is 1 second per 10 feet of length, or 4 seconds for a 40-foot bus. Because the bus is going faster than 40 mph, add 1 second, for 5 in all.
Smaller, lighter vehicles generally need less distance to stop than a heavy commercial vehicle. Leave extra space behind them so a sudden stop does not catch you short.
The arrows above and below the posted height show the lowest clearance under a bridge, overpass or similar structure ahead. If you drive a tall vehicle like a truck, bus or RV, compare that figure with your vehicle's height before going on.
Slippery pavement means it takes much longer to stop, so the spacing that works on dry roads falls short. Keep far more room than the normal guideline of a second for each 10 feet of length, plus one extra second above 40 mph.
Every question in this set has its own page with the correct answer and an explanation.
