whilst cycle helmets are not mandatory, in rio, they do give cyclists an extra level of protection and are a must have - due to the heat of local weather, carrying water is advised, to avoid exhaustion - even on cloudy days, the heat can result in quick exhaustion, thus riders should always bring along a bottle of water, and sunscreen to prevent sunburns.  

as rio de janeiro is such a busy metropolis, picking the right time to go for a cycle can also help comfort and safety - weekends and holidays are generally considered the best time to cycle in rio, as some of the avenues such as avenida atlantica, are closed, for sports.

overall, rio de janeiro is a safe place to go bicycling, and is very welcoming to those who opt to cycle over less environmentally-friendly forms of transport, but taking the necessary precautions helps to avoid any problems, is always a good option.