The PSNI and Garda are urging motorists to take extra care after several reports of black ice in both Derry and Donegal on Wednesday morning.
Two cars left the road and landed in a ditch on Groarty Road in Derry.
There were also several reports of minor crashes involving black ice across Co. Donegal.
"Motorists are asked to exercise extreme caution when driving tonight as there may be patches of ice on the roads," said the PSNI in Foyle.
"Drive carefully and arrive at your destination safe and sound."
What should I do if I encounter black ice?
1. Anticipation and smoothness are key for driving on icy roads.
2. Look well ahead for potential hazards – including, of course, patches of ice – and keep your speed well down.
3. Accelerate, brake, steer and change gear as smoothly as possible to reduce the risk of a skid.
4. A higher gear may be more appropriate to aid grip on packed ice.
5. This helps manage engine power delivery, making it easier to find traction. If it’s a manual, you might need to slip the clutch a little to prevent the car from stalling.
6. Many automatics will let you select second gear at a standstill to pull away in.
(Courtesy of Royal Automobile Club (R.A.C.)