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Managing Speed

Teen Crash Fact

"Driving too fast for conditions" is the No. 1 reason 16- and 17-year-old drivers are involved in crashes.

What is a safe speed? How fast is too fast? There are no simple answers to these questions because there is not a single speed that is safe at all times. In addition to the posted speed limit, you must consider road conditions, visibility conditions, and the flow of other traffic in choosing a safe speed to drive. Also, when you plan to change speeds, it will help you stay safe, by communicating your intentions to other drivers.

Posted Speed Limits

Posted speed limits indicate what the maximum safe driving speed is under the ideal road, traffic, and weather conditions.

  • The maximum speed limit in Pennsylvania is 70.
  • The maximum speed limit on interstate highways is posted after each interchange.
  • On other highways, the maximum speed limit would be posted at approximately ½-mile intervals.
  • In school zones, the speed limit is 15 mph when the lights on the school zone sign are flashing or during the time period indicated on signs. School zone speed limits are lower than other speed limits.

When the road is wet or slippery, when you cannot see well or when anything else makes conditions less than perfect, drive below the posted speed limit. Even if you are driving within the posted speed limit, you can still be ticketed for driving too fast for conditions.


Safe driving does more than protect you: it saves you money and reduces air pollution. Operating a car involves many expenses, including gas, maintenance, and tires. Drivers and car owners can take a number of steps to minimize these expenses at no additional cost.

Smart Driving Habits to Adopt

  1. Slow down. Fuel consumption increases about 5 percent for every five miles per hour driven above 60 mph.
  2. Ease up on the pedals. Rapid starts and hard stops can increase fuel usage by 40 percent, but reduce travel time by only 4 percent.
  3. Drive cool. Avoid driving during the hottest parts of the day. Cooler, denser air can boost power and mileage.
  4. Stay cool. Use your car's air conditioner when driving more than 40 mph.
  5. Drive to warm up. Even on the coldest days, it only takes 30 seconds to get your vehicle ready to drive.
  6. Keep cruising. Get 7 percent average fuel savings by using cruise control while driving on flat highways.
  7. Follow the light. When your vehicle's on-board diagnostics (OBD) light turns on, it is possible that fuel economy is decreasing and emissions are increasing. If the OBD light comes on, talk with your auto dealer for more information.
  8. Drive safely. Keep enough distance between you and other vehicles. Doing so not only protects you, it also prevents wear and tear on your vehicle.
  9. Utilize your car. If your vehicle has an "ECO" setting, use it. It will smooth out your gas pedal inputs, optimize transmission shift points, and decrease the impact of air conditioner on the engine.
  10. Turn it off. Idling wastes fuel and may be prohibited. If you need to idle, shift to neutral or park so the engine is not working against your brake and consuming more fuel.
  11. Drive less. There are multiple ways to reduce costs and save money by driving less. Take public transportation, bicycle or walk, or carpool. Additionally, combining errands saves time and gas.
  12. Educate yourself. There are many resources available to get and stay educated about the best safe driving practices.

Driving At Night

The highest crash rates occur during nighttime hours. Most serious crashes occur in twilight or darkness. Overall, traffic fatality rates are three to four times higher at night than in daylight. Compared to driving in the day, driving at night is more dangerous.

There are several reasons for this:

  • Your vision is severely limited at night.
  • Glare from other vehicles' headlights may temporarily blind you.
  • More people who are tired or who are driving under the influence are likely to be on the road at night.

With less light, your ability to judge distances is reduced, your ability to see colors is reduced, and your ability to see things in your side vision is reduced. As a driver, you must always be ready to react if you suddenly see something unexpected on the road ahead of you — a pedestrian, a bicyclist, an animal, etc. — and you are much more likely to be surprised at night. Compared to signs and other roadside objects, pedestrians are the hardest to see at night.

You must use your headlights properly at night and other times, as required by law. Headlights have a dual purpose: to help you see and to help you be seen. Clean your headlights at least once a week. Do it when you buy gas for your vehicle — dirty headlights may give only half of the light they should.

State law requires drivers to use their headlights:

  • When they cannot see because of insufficient light on gray days or in heavy traffic when their vehicle may seem to blend in with the surroundings.
  • When there are unfavorable atmospheric conditions, including rain, snow, sleet, hail, fog, smoke or smog. In bad weather, use only low beams. High beams actually reduce visibility under these conditions.
  • When they cannot see pedestrians or vehicles on the highway for a distance of 1,000 feet ahead of the vehicle they are operating.
  • Between sunset and sunrise.
  • When driving through work zones.
  • Anytime your vehicle's wipers are in continuous or intermittent use due to weather conditions.

NOTE: Daytime running lights are not enough. Your tail lights must be illuminated as well.

State law calls for fines beginning at $25 and with other associated costs, the penalty would approach $100 for drivers who fail to use their headlights when required!

Other important safety information about headlights and nighttime driving:

  • When driving at night, use low beams as soon as you see another vehicle approaching in the oncoming lane, as high beams can "blind" the other driver. Pennsylvania law requires you use low beams whenever you are within 500 feet of an oncoming vehicle and when you are following a vehicle within 300 feet.
  • If a vehicle using high beams comes toward you, flash your high beams quickly a few times. If the driver does not dim their lights, look toward the right side of the road. This will keep you from being "blinded" by the other vehicle's headlights and will allow you to see well enough to stay on your course until the vehicle passes.
  • Do not try to punish the other driver by keeping your bright lights on. If you do, both of you may be "blinded."
  • If glare from a following vehicle's headlights is uncomfortable because it is reflecting in your rearview mirror, you can switch the inside rearview mirror from its daytime to nighttime setting.
  • Do not "overdrive your headlights" by driving so fast you could not stop in time to avoid a hazard that appears within the length of road ahead lighted by your headlights. Low beam headlights shine only about 250 feet ahead. Even on dry pavement, it takes more than 250 feet to stop if you are moving at 55 mph. To avoid overdriving your headlights on a dark road at night, you should not drive faster than 45 mph.

Road Conditions

Your ability to stop is greatly affected by the condition of the road. You need to reduce your speed when road conditions are poor, so you can maintain control of your vehicle. You will be at greatest risk if you drive too fast on roads that are slippery, especially on curves. Take turns and curves more slowly when the road is slippery.

Wet Pavements

All roads are slippery when wet, but be extra careful on roads posted with warning signs that say SLIPPERY WHEN WET. Pavements can become very slippery in the first 10 to 15 minutes of a rainstorm. The rain causes oil in the asphalt to come to the surface. This problem becomes even worse during hot weather, when the heat combined with the water causes more oil to rise to the road surface. In cold, wet weather, be extra careful driving on sections of road shaded by trees or buildings; these areas freeze more quickly and dry last.


At excessive speeds, your vehicle can begin to hydroplane on a wet roadway. Hydroplaning happens when your tires lose their grip on the road and ride like skis on a film of water. The faster you drive on a wet roadway, the less effective your tires become at wiping the water from the road. You can hydroplane at speeds as low as 35 mph, when water is only 1/10 of an inch deep. Worn tires make this problem worse. Hydroplaning can be reduced by driving slower.

If you find yourself hydroplaning, do the following:

  1. Keep both hands on the steering wheel.
  2. Slowly take your foot off of the gas pedal to let your vehicle slow down. Do not slam on the brakes or try to turn suddenly because this will cause your vehicle to skid. As your vehicle slows down, the amount of tire tread touching the road will increase, and you'll begin to get better traction.
  3. Turn slowly and only as much as necessary to keep your vehicle on the road.
  4. If you have to use your brakes, brake gently. (Refer to the section "If you have to brake suddenly," later in this chapter for important information about using conventional versus anti-lock brakes in emergency stops.)

Snow and Ice

When driving on snow or ice, you will need to adjust your driving to accommodate any situation. The traction of your tires on the road will be greatly reduced, seriously affecting your steering and braking ability. Also, it is extremely dangerous near 32° (Fahrenheit), when precipitation turns to rain or sleet — a thin layer of water on top of ice is more slippery than ice alone.

Watch for "black ice," a condition occurring on clear roadways when a thin layer of ice forms due to dropping temperatures. When the road looks wet but no spray is coming from the tires of other vehicles, "black ice" may be present.

Under law, which went into effect July 10, 2006, motorists will face severe fines if snow or ice that falls from their vehicle causes injury or death to other motorists or pedestrians. When snow or ice is dislodged or falls from a moving vehicle and strikes another vehicle or pedestrian causing death or serious bodily injury, the operator of the vehicle from which the snow or ice came is subject to a fine of $200 to $1,000 for each offense. PennDOT urges motorists to remove all ice and snow from their vehicles before traveling.

When roads get slick, you should:

  • Reduce your speed by 5 to 10 mph on wet roads and increase your following distance to five or six seconds.
  • On ice or snow-covered roads you need to slow down even more. On packed snow, decrease your speed by half; on ice, slow to a crawl. Leave about 10 times more space than normal between you and the vehicle ahead.
  • Apply brakes gently, ease off if you start to skid, and reapply when you regain control. (Refer to this section "If you have to brake suddenly," later in this chapter for important information about using conventional versus antilock brakes in emergency stops.)
  • Do not use your cruise control when driving on slippery roads. Snow, ice, slush, and rain can cause wheel-spin and loss of control. The only way to stop wheel spin and regain control is to reduce power. But, an activated cruise control system will continue to apply power, keeping your wheels spinning.
  • Adjust your speed to avoid meeting other vehicles in slippery areas, such as shady spots and frost on bridges during cold weather. This will reduce the risk of skidding into the other vehicle.
  • On icy or snow-packed roads, try to time your arrival at an intersection by letting your vehicle coast until the light turns green and vehicles ahead of you have begun to move. This way, you will not have to brake to stop and then accelerate to begin again. Also, when going uphill, stay far enough behind the vehicle ahead, so you will not need to slow down or stop. Before starting downhill, shift to a lower gear for better control.

Visibility Conditions

In addition to nighttime, fog and snow are conditions that reduce visibility and can dramatically decrease your ability to see ahead, and to respond quickly and safely to events happening around you.

Fog is probably the most dangerous driving environment. You cannot see what you are about to hit, and others cannot see you either.

Do not start a trip if the fog is so dense you cannot see. If you get caught in dense fog, it’s best to pull completely off of the road, preferably into a parking lot, to wait until the fog clears. While parked, turn your hazard lights on to make your vehicle more visible, and keep your seat belt fastened.

When you must drive in FOGGY CONDITIONS, always remember to do these two things:

Slow down enough so you can stop safely within the distance that you can see. You will need to carefully check your speedometer because fog takes away most of the visual information that lets you know how fast you are going; this makes it easy for you to speed up without being aware of it.

Turn on your low beam headlights (and fog lights, if your vehicle has them) so others can see you. Do this whether it is daytime or nighttime. Do not use your high beams. They direct their light up and into the fog, which bounces the light back into your eyes, creating glare and making it even harder for you to see ahead.

Snow also can severely limit your visibility.

To increase your ability to see when driving in SNOWY CONDITIONS, do these six things:

  1. Clear all the windows, hood, trunk, and roof of your vehicle before starting to drive in the snow. If you don’t, snow will blow off of your vehicle and onto your windshield, blocking your view, or could blow off and onto the windshield of a driver who is following you. If snow or ice from a moving vehicle strikes another vehicle or pedestrian causing death or serious bodily injury, the vehicle’s driver could be fined.
  2. Clear your headlights, taillights and directional signals of snow, ice, and dirt. This helps other drivers see you and helps you see what is ahead. A dirty headlight reduces light output by more than 50 percent.
  3. Let the engine warm up before you start driving. It gives the defroster a chance to warm the windshield and melt any ice you could not scrape off.
  4. Use your windshield wipers to keep your windshield as clear as possible. Make sure your windshield washer reservoir is full, and you are using fluid that will not freeze.
  5. Keep the defroster on to clear steamed windows. If you have a newer vehicle, your defroster may be part of your air conditioning system. Read your owner's manual to learn how your vehicle’s defroster settings should be used.
  6. Turn on your low beams, even during the daytime. This increases your visibility to other drivers.

Headlight / Windshield Wiper Law

This law, which went into effect Jan. 28, 2007, requires motorists to turn on their headlights anytime their vehicles wipers are in continuous or intermittent use due to weather conditions. Daytime running lights are not enough. Your tail lights must be illuminated as well. Motorists who do not comply with the law may face a fine of $25, but with fees and other associated costs, the penalty would approach $100.

Traffic Flow

  • Crashes often happen when some drivers go faster or slower than other vehicles on the road. Always try to drive with the flow of traffic within the posted speed limit.
  • You may need to adjust your speed to maintain your space cushion depending on what traffic is doing around you. For example, when traveling in a pack of vehicles on a highway, you will often find yourself traveling in someone’s blind spot with no space cushion for emergencies. When this happens, reducing your speed by just 2 or 3 mph will encourage traffic around you to clear out, so you are no longer closed in.
  • Another time when you may have to adjust to traffic flow is if there is more than one potential hazard ahead you will confront at the same time. For example, with a bicyclist to your right, the safe thing to do is to move left to allow a wide margin when you pass. But, if there is also an oncoming vehicle, this creates a problem because normally you would want to move to the right in your lane in this circumstance. You should handle this situation by facing only one traffic condition at a time. Slow down to let the oncoming vehicle pass and then move left to pass the cyclist, leaving a sufficient amount of space for safety.
  • Also, when you are approaching an emergency scene, police stop, or a tow truck picking up a disabled vehicle, you must move into a nonadjacent lane. If you cannot move over, you must slow to a careful speed.

Handle only one traffic condition at a time.

Slow down behind the bicyclist, let the oncoming vehicle pass, and then move left to pass the cyclist, leaving at least 4 feet of space for safety.

Reactions To Slow-Moving Traffic

Watch out for vehicles that have trouble keeping up with the flow of other traffic and when entering the roadway; they take longer to pick up speed. These include some large trucks, as well as farm equipment and horse-drawn vehicles. Trucks, especially on long or steep upgrades, typically use their flashers to alert other drivers they are moving slowly.

In rural areas, an orange triangle is displayed on the back of farm tractors and horse-drawn vehicles designed to operate at 25 mph or less; this is a slower speed than traffic normally travels. In certain areas of Pennsylvania, it is not at all unusual to find yourself sharing the road with farm tractors and horse-drawn vehicles. Stay a safe distance back, and do not honk to pass.

Communicating Your Intentions To Other Drivers

Crashes often happen because one driver does something that another driver does not expect. To help avoid crashes, communicate with drivers on the road.

Let others know where you are and what you plan to do by:

  • Signaling when slowing down or stopping. Your brake lights tell other drivers you are slowing down or stopping. If you are going to brake where other drivers may not expect it, quickly tap your brake pedal three or four times. If you must drive below 40 mph on a limited access highway, use your hazard (four-way) flashers to warn the drivers behind you.
  • Signaling when changing direction. Signaling tells others you want to make a turn, but it does not give you the right to make a turn. Under Pennsylvania law, you must always use your turn signals at least 100 feet before turning, if you are driving less than 35 mph. If you are driving 35 mph or more, you must signal at least 300 feet before turning. If your vehicle’s turn signals do not work, use these hand signals.
  • Using emergency signals. If your vehicle breaks down on the highway, you will need to pull off the road. Signal, then carefully exit the roadway, and put on your hazard (four-way) flashers to warn other drivers. Get as far off of the road as possible, and park in a place where other drivers can see you easily. Lift your hood to let other drivers know your vehicle is disabled.
  • Using your horn. Your horn instantly attracts the attention of other drivers. Use it when you think another driver or a pedestrian does not see you – for example, if a child is beginning to run into the street or if you think another vehicle is about to hit you. Also, if you lose control of your vehicle, alert other drivers by sounding your horn.

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