On Friday night, February 25, a car mowed through approximately 150 cyclists attending a Critical Mass ride in the fourth most populous city of Brazil. About 20 riders were injured and eight were sent to hospital.

The attack raises the alarm about the importance of safe bike infrastructure for cyclists. It also raises questions about whether the Critical Masses that take place require police accompaniment.

Certainly, the many massers that gather in cities across the world should be free to continue spreading the word about the joys of cycling in cities and the need for proper infrastructure to support this pursuit. It's the problem of cyclist-motorist conflict that continues to spur debate and raise concerns among cyclists, motorists and policy-makers alike.

Some motorists complain about the fact that Critical Mass often slows down traffic along some routes and prevents vehicles from passing through intersections being blocked by the unofficial parade.

Massers, on the other hand, are concerned about the safety of riders, which is the reason given for wanting to stick together as a group.

One possible solution is the development of complete streets where cyclists, motorists, mass transit users and pedestrians are all given equal weight in the design of city transportation infrastructure. The other option is to foster a "share the road" mentality. It doesn't necessarily have to be an either/ or situation. Motorists and cyclist can share road space.

Protective barriers and proper infrastructure at intersections can improve cyclist safety. Ultimately, though, attitudes about cycling in North America need to reflect a shared concern about the safety of all road users.