4.6 Interstate & Limited-Access Highways: Entering, Exiting & Stopping

What Limited-Access Highways Are

Limited-access highways are large roads with no intersections or traffic lights and a limited number of places to enter and exit. An interstate is a limited-access highway that crosses from one state to another; I-95, I-70, I-695 and I-495 are Maryland examples. Speed limits above 55 mph may be set only on interstates and expressways, up to a maximum of 70 mph. Bicycles are not expected on interstate highways, and mopeds may ride only on roads posted 50 mph or less.

Entering the Highway

You usually enter by an entrance ramp and an acceleration lane:

1. On the ramp: look for a gap in highway traffic through your mirrors and over your shoulder.
2. In the acceleration lane: adjust your speed to the flow of traffic already on the highway.
3. Merge: signal and move into a gap. Drivers already on the highway have the right-of-way.

The manual adds that when entering you should not cross the solid lines that divide the entrance from the highway; wait until the lines are broken. Avoid stopping at the end of the acceleration lane unless traffic leaves you no choice, because merging from a stop at highway speed is dangerous.

Highway drivers can help by moving left, when it is safe, to make room for merging traffic.

Driving on the Highway

• Slower traffic keeps right. If you are driving slower than traffic on the highway, drive in the right lane whenever possible.
• Keep at least a 3-to-4-second following distance, and more in bad weather or behind large trucks.
• Avoid driving in a truck's blind spots (see Section 6.3), and pass on the left.
• Look far ahead. Brake lights several vehicles ahead give you time to slow smoothly.
• Watch for highway hypnosis, a drowsy, trance-like state on long, monotonous drives. Take breaks and switch drivers (see Section 5.4).

Exiting the Highway

1. Move to the right lane well before the exit you plan to take. Overhead signs show which lanes lead to which exits.
2. Start slowing as soon as you enter the deceleration lane, not in the travel lanes. The deceleration lane leads to the exit ramp and gives you room to slow.
3. Keep slowing to the posted speed for the exit ramp; advisory speed signs show a safe ramp speed.

If you exit at the wrong place, continue until you are off the exit ramp, then look for a way to re-enter the highway. Never stop and back up on any part of the highway, including the shoulder and ramps. Median crossovers are for authorized emergency and maintenance vehicles only.

Interchanges and Toll Plazas

• Weaving areas: where an entrance ramp and an exit ramp share a lane, drivers are entering and leaving at the same time. Adjust speed early, signal, and do not make last-second lane changes.
• Left exits and splits: read overhead lane-use signs early so you are in the correct lane before the road divides.
• Toll plazas: the manual lists toll plazas among the places to reduce speed. Choose your lane early, watch for vehicles changing lanes, and keep a safe following distance.

Stopping on the Highway

You are not allowed to stop in the lanes where traffic is moving on an interstate or other highway. You may stop on the shoulder only if your vehicle is disabled (stops running) or you have another emergency. If you must stop:

• Turn on your emergency flashers to warn other drivers.
• Stay inside your vehicle if you can, with your seat belt on. Standing or walking along an interstate is very dangerous because traffic is moving at very high speeds.
• If possible, get to an off-ramp or parking lot instead, even on a flat tire.
• Never stop or park in the triangle-shaped painted zone where a ramp leaves the road.
• Use the nearest mile marker to tell 911 or a tow service where you are.

If staying in the vehicle is not safe, the manual says to pick the safest moment, get out, move away from the road, and get behind a barrier or guardrail, ideally on higher ground (see Section 7.3).

Scenario Practice

1. Your acceleration lane ends soon and traffic is heavy. Adjust your speed to line up with a gap, signal and merge; do not cross the solid line early.
2. You realize you took the wrong exit. Continue to the end of the ramp, then find a legal way back.
3. Your engine dies in the center lane. Turn on your flashers and coast to the shoulder if you can; stay buckled inside and call for help using the mile marker.