With three deaths already on open roads this week, the roads policing unit is issuing an urgent appeal to riders and motorists to take extra care.
They say that means travelling at the right speed for the road conditions and riding within your own ability.
Inspector Terry Stephen says the recent warm weather has probably tempted more riders than normal to go out for a lap.
And he's stressing that roads around the course can still be busy with traffic first thing in the morning.
Three-week road closure for gas main works
Stretch of Ballakermeen Drive shut until 28 September
Public expectations for high street services 'a contradiction'
Political commentator says locals expect services to be efficient but for nothing to change
Info Commissioner partially upholds terminal complaint
Other exemptions applied were handled correctly
MGP organisers ACU respond to accusations of 'hollow promises' following rider's death
Sam Naughton was killed after an incident at Doran's Bend at this year's event