They claim cars and taxis frequently block lanes intended for bicycles, making it harder to get around the city on two wheels and endangering cyclists by forcing them to pull out into traffic.
Members of the campaign group CycleSheffield have shared dozens of examples of such inconsiderate parking, many of which are in 'mandatory' cycle lanes bordered by unbroken white lines, within which it is illegal to drive or park.
He wants to see more mandatory lanes, and ideally ones which are physically segregated from other traffic, to improve safety and encourage more people to take to their bikes.
"If people park in cycle lanes, cyclists are forced to pull out to pass those vehicles, which can be dangerous, and there's the added hazard of being hit by a door opening, which has happened to me on Ecclesall Road," he said.
"Drivers will park where it's most convenient, regardless of the impact on cyclists, unless you prevent them doing so physically, for example by putting bollards in place, or by fining those who are caught."
Mr Johnstone added that he believes the council should do more to enforce mandatory cycle lanes, and he urged more people to report illegal parking in those lanes.
The group recently secured a small victory in its battle to make Sheffield more bike-friendly, after Sheffield Council agreed to ban parking along Clarkehouse Road, near the Royal Hallamshire Hospital, where the cycle lanes are often blocked by cars.
"We are also the first city outside of London to use 'Orcas' - mini humps separating cycle lanes from other traffic - to keep cyclists safe.
"We know there is more to be done here and I’m pleased to see us moving away from simply painting lanes on the road. This will reduce conflict between user groups."
The hot spots for parking in cycle lanes highlighted by members of Cycle Sheffield included: Penistone Road, in Hillsborough; Castle Street, in the city centre; Glover Road in Highfield; the Wicker; and Ecclesall Road.
Michael Wall said he had to put up with motorists driving and parking in mandatory cycles, or taking up the designated boxes for cyclists at traffic lights, and he claimed taxi drivers were among the worst culprits.
"Mandatory cycle lanes carry a £1,000 fine for motorists driving or parking in them, but I see little evidence that the message is getting through to motorists, and I don't think that will change unless more fines are issued." added the 63-year-old retired careers advisor, from Walkley.
* You can report cars seen driving or parking in mandatory cycle lanes to email [email protected]