Perth drivers have been warned their Thursday morning commute may take longer than usual, with Main Roads still struggling to fix a traffic signals glitch.

Despite technicians working to restore around 145 intersections on Wednesday, Main Roads said traffic light timing issues were still being experienced in some areas.

While the majority of traffic lights have been fixed, some signals are not working as they should during peak hour. Credit:STAFF

The fault was triggered after maintenance carried out on the system's software on Tuesday night, with the system failing to work properly once Main Roads switched it back on.

Main Roads spokesman Dean Roberts said instead of these traffic lights working in a responsive manner, with traffic signals triggered when the sensors registered a waiting vehicle, the intersections had reverted to their automatic settings.