It happened just after noon close to the 1 mile marker where the trail crosses West Enterprise Street.
The woman told police a man approaching from the opposite direction flashed them as they passed.
The suspect was described as a black male in his 20s, approximately 6 feet tall and 180 pounds with short hair. He was wearing a black jacket and dark jeans.
A similar incident happened on the trail earlier this month.
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The Durham Police Department has following personal safety tips:
-Be aware of your surroundings
-Call 911 to report any suspicious activities
-Do not walk alone
-Try to remain in well-lit areas
-Trust your instincts
-Do not walk/run with earbuds or headphones
-Bring a cell phone
Anyone with information is asked to call CrimeStoppers at (919) 683-1200. CrimeStoppers pays cash rewards for information leading to arrests in felony cases and callers never have to identify themselves.