DOI says they're to be used when emergency vehicles need priority
Extra signs are being put up this year to warn of the potential use of traffic lights on the TT access road.
During practices and races, the road between Quarterbridge and Braddan can be used to get in or out of the course.
It's also the main route for emergency vehicles, and traffic lights are often used to allow them to pass safely and without delay.
The Department of Infrastructure says it's putting up extra signs to explain this and ask for patience and understanding from other road users.
No public board meeting for Manx Care due to General Election
Chauffeur needed to provide 'professional and discreet service' for VIPs
Fire officer praises 'quick-thinking' staff after blaze at fire station
Chief Minister: 'AG not out to silence debate'