Police have increased patrols along the Taff Trail in Cardiff after reports of a number of robberies.
Officers say they are investigating seven robberies in the last five weeks.
All the incidents took place during the hours of darkness between 8pm and midnight and were near the Cardiff city centre end of the trail.
A spokesman for South Wales Police said: "Patrols are being stepped up in the area but we'd also urge everyone to take normal precautions whenever they're walking in unlit or poorly-lit areas.
"In the hours of darkness we always encourage people to stick to well-lit, busy roads."
The trail is a popular route for cyclists, walkers and runners, but it is poorly lit in places.
During the day it can be extremely busy but it can be very quiet in the evenings and after dark.
Staff at Cardiff Metropolitan University have gone so far as to urge students to use alternative routes in and out of the city.
A statement said: "We have been made aware of a rise in robberies on the Taff Trail recently. South Wales Police has recommended using alternative routes in and out of the city at this time.
"Please report any incidents to the police. Dial 101, or 999 in an emergency."
The trail is close to student accommodation for thousands of people who attend different universities in the city.
