The Ashman Phenomenon refers to the behavior of driving observed in roundabouts where drivers tend to slow down, or stop at the entrance instead of going at their planned speed.

The Origin of Ashman Phenomenon

The term Ashman Phenomenon was created by an British traffic engineer Mr. Howard Ashman, who first noticed this phenomenon in the 1970s.

What's the reason the Ashman Phenomenon Take Place?

The root of the Ashman Phenomenon's cause is not yet known, but there are several theories that suggest that the behavior is caused by drivers' confusion over their primary concern or obligation to surrender to other road users.

Impact of Ashman Phenomenon on Traffic Flow

The Ashman Phenomenon could create significant delays and interruptions to traffic flow, as well as increased fuel consumption and emissions due to drivers slowing down and accelerating.

Countermeasures to Reduce Ashman Phenomenon

To minimize the Ashman Phenomenon, it is crucial to educate drivers on the rules and expectations for roundabouts. It is also important create roundabouts that have uniform and clear indications and signs.


The Ashman Phenomenon is an intriguing and complicated driving style that continues to challenge researchers and traffic engineers. While the cause remains unknown but it is obvious that the behavior can have a significant effect on traffic flow and the environment.