Due, in part, to the changes in traffic behavior, many intersections do not accommodate some
common traffic patterns very well. Heavy turning movements are often a problem at
intersections. Many intersections now need three lanes for left or right turns, which can cause
safety and operational problems. Some of these intersections need to be grade-separated, which
can be costly. When there is heavy directional movement in more then one direction, most
intersections have difficulties accommodating the traffic. If the heavy movements are both ways
along the same road, there are often synchronization problems with other signals on the road.
The intersection designs are also engineered for a strong hierarchy of intersecting roads. For
example, an arterial road normally intersects collector roads at signals. However, there are many
cases where the two heavily utilized arterials or intersect, which makes designing intersections
and interchanges even more difficult.