This is the first time such maps are being used in Hong Kong, and they come 10 years after panels showing estimated journey times on congested routes were installed.

The Transport Department says it hopes the panels will help drivers pick routes and even out traffic among them.

Assistant Commissioner for Transport Leung Tak-fai , said 134 speed detectors along the routes would send data to a system that would determine traffic flow.

The information will be updated every two minutes and can also be obtained from a new smartphone application or the department's website.

Leung said about 123,000 cars a day use the routes, which have a total length of 99.27 kilometres.

"The maps are simple and easy to understand. We believe the drivers will get an idea of the car flow in one to two seconds, so we are not worried they will be distracted and cause accidents," Leung said.

He said the department picked New Territories East and West to start with because of the heavy flow of traffic there.

The department would monitor the system and see if there was any need for fine tuning before extending it to other districts, Leung said, warning that there could be inaccuracies in the beginning.

Car plates would be registered to determine speed, but the department said the information would not be used in speeding prosecutions, and only plates registered by companies would be used due to privacy concerns.

Leung said the system was designed in 2009 and construction was completed last year.