The city's streets got meaner last year for bicycle riders, who were killed at a rate of nearly two a month in deadly collisions.Traffic accidents claimed the lives of 21 bicyclists – up from 15 in 2004 – a 40% rise, police statistics show. There were 16 fatalities in 2003."The increase in bicyclists killed last year is of great concern to us and we're working with the Police Department and advocacy groups to initiate a bicycle safety outreach campaign," Transportation Department spokeswoman Kay Sarlin said.All too often, drivers don't watch out for bicyclists, Noah Budnick of Transportation Alternatives said. He called for a police crackdown on reckless driving.But the police don't believe there is a grim upward trend taking place. The number of such fatalities tend to fluctuate year to year, Deputy Inspector Michael Coan said, pointing out that 35 cyclists were killed in 1999.The increased popularity of cycling may be playing a role in the higher death toll. Transportation Alternatives estimates that 120,000 people cycle each day in the city, which the group believes is an all-time high.The city Health and Transportation departments are studying biker fatalities, hoping to better understand contributing factors, such as speeding and failure to wear helmets, Sarlin said.The city also will continue to increase safety by measures that include establishing bicycling routes with protective barriers, Sarlin said.There were 312 traffic fatalities last year. That number encompasses drivers, passengers and pedestrians, in addition to bicyclists, and reflects a 5% increase over 2004.But traffic fatalities had declined steadily for more than a decade and the 2005 tally was the second-lowest since 1910