"This animation shows a diamond interchange linking a main highway with a local road. Notice the tight spacing of ramp terminals at the interchange…those places where entrance and exit ramps meet the local road. Immediately off the interchange is a cross-street with a traffic signal...and the local road is lined with driveways, meaning vehicles can turn into or out of traffic at numerous points.

When ramp terminals are too close to each other, the result is usually congestion. This kind of spacing creates a number of problems:

• When traffic signals are located at both terminals, it takes more time for thru-traffic to get through the interchange.
• During peak traffic, the line of vehicles waiting to turn left onto the highway can grow long. This congestion may interfere with thru-traffic and with vehicles leaving the exit ramps.

Congestion can also result when a cross-street is located too close to an interchange:

• A traffic signal at this location can keep vehicles from clearing the area, and traffic becomes bottled up around the interchange.
• Traffic flow can also be affected when vehicles leaving the exit ramp, must cut across lanes of traffic to make the quick left turn.

Traffic flow and overall safety can be greatly affected by a large number of driveways which increase the number of conflict points on a roadway, as well as the risk of crashes. And any kind of incident or obstruction in this setting can turn congestion into gridlock."