The yellow trap occurs when the timing of the amber lights (also known as "yellow" lights in the USA) is asymmetric for two-way traffic on a single road: when a vehicle is waiting to turn across oncoming traffic and receives an amber light from the traffic signal, the driver may assume that oncoming traffic also has received an amber light and proceeds with the turn, believing that oncoming traffic will yield the right-of-way on an assumed amber.
The yellow trap happens when the timing of the amber lights (also referred to as "yellow" lights in the USA) is uneven for two-way traffic on a single road: when a vehicle is waiting to turn across oncoming traffic and receives an amber light from the traffic signal, the driver may assume that oncoming traffic also has received an amber light and proceeds with the turn, believing that oncoming traffic will yield the right-of-way on an assumed amber.