A woman who sustained critical head injuries when she fell off her electric bike in Bruce on Monday is believed to have hit a pot-hole.
The woman was travelling towards the city on Belconnen Way, close to the Barry Drive intersection, when she came off the bike about 8am.
Paramedics took her to the Canberra Hospital.
ACT Policing's acting officer in charge of traffic operations Tracey Duck said there weren't any other vehicles involved in the incident.
"The woman merely fell off the bicycle, she appeared to have hit a pot-hole and that caused her to fall off her bike," she said.
She said the woman had been wearing a helmet at the time.
The incident prompted Sergeant Duck to warn motorists electric bikes could travel at high speeds and were much more powerful than a push bike.
"They generate a lot of power and people go too fast for the conditions, especially on the side of a road where there may not be a designated bike path.
"This is a reminder for people who do have electric bikes that they are quite dangerous, that they do have a lot of power."
Police have called for anyone who witnessed the incident to come forward as they continue to investigate.
Contact Crime Stoppers on 1800 333 000 or at act.crimestoppers.com.au.