London, Aug 13 (IANS): A new iPhone app alled Canary has been developed to prevent people from getting behind the wheel after smoking marijuana.

Created by former engineer Marc Silverman, the app aims to test mental and physical performance of the user in four steps, Daily Mail reported.

The app tries to test balance, memory, reaction time and time-perception using fast game-like activities.

Users start by establishing a base line when they are sober, which all other results will be measured against.

On the left, numbers appear and the user has to remember the order in which they appear. On the right is a time-reception activity.

After completing all four, the results are put against the baseline for a green, yellow or red light as to whether the user should be driving.

Then, the users can check again when 'stoned' to see the effect that marijuana is having on them.

The app costs $4.99 in the App Store.

Silverman said that he is marketing the app for marijuana smokers and not as a tool for law enforcement.