The NYT reports the following:
Businesses will have to give bicycle delivery workers helmets, require that they wear them and use bikes with safety equipment required by state law, including brakes and reflectors. (That means that messengers can't use track bikes with no brakes.) The new laws take effect on July 26.
http://www.nytimes.com/2007/03/29/nyregion/29mayor.html?ref=nyregion