"Any time a cyclist is killed, a white bike is put in that place as a reminder to vehicles and other cyclists to be careful and watch out for cyclists on the road," she said.
"It's a memorial for Jane and also a reminder for others, and it's really fascinating when we put it up, how many people did a huge diversion onto the other side of the road to pass, so it does actually work."
The ghost bike was installed a year to the day after Mrs Farrelly's death.
A ghost bike has also been installed on Auckland's waterfront, where Jane Bishop died after she collided with an open car door and fell under a truck.
An inquest into Mrs Farrelly's death is expected to be held in Hamilton in July.
Ms McCullough is also organising a petition to take to Parliament, calling on it to change the law to require motorists to give at least 1.5m passing distance to pedestrians and cyclists. She hopes to get up to 20,000 signatures.
The petition can be found at www.change.org by searching "protection for walkers and cyclists".