Little Yellow Trap and Green Trap

Two more traps to be aware of

What is Little Yellow Trap?

Little yellow trap is when the circular greens for both directions end at the same time, but the circular yellows do not.

What happens in little yellow trap?

When the shorter yellow turns red, the driver thinks the other direction is red too, and completes his turn. Although it is unlikely to happen, an oncoming straight-ahead driver could continue on through during this period, causing a crash.

When does little yellow trap happen?

Little yellow trap happens whenever the yellow clearance intervals of the two circular green phases are set to different values.

What can be done to prevent little yellow trap?

1. Make sure the yellow clearance intervals on both circular green phases are set to the same value.

2. If there are no turn arrows on the street, use the same phase unit for both circular greens.

Permissive turns on green
One yellow ends earlier

What is Green Trap?

Green trap occurs where there are no left turn phases, but the circular greens facing opposite directions can start at different times. This can fool a left turning driver when an opposing driver suddenly gets a circular green and starts to move.

What happens in green trap?

A left turning driver sees an oncoming car slowing down for a red signal, so he thinks he has the right-of-way. As the oncoming driver enters the detector, his signal suddenly turns green, and he starts to move to go straight or right. He enters the intersection in the path of the left turning vehicle. This can cause a crash.

When does green trap happen?

Green trap happens when opposite circular greens on the same road have their own phase units, but no other phase units are in the concurrency group. The problem happens when one phase stays red until a car appears on the approach.

What can be done to prevent green trap?

1. Use the same phase unit for both circular greens.

2. Force display of concurrent greens.

Permissive turn on circular green
Permissive turns on circular green trap