Autorickshaws and private buses are responsible for the snarls on city roads, a Besu study has revealed. The study, commissioned by the Calcutta Municipal Corporation (CMC), was conducted by the transportation engineering and planning wing of the civil engineering department under the leadership of Prof Sudip Roy. "There are over 100 auto routes in the city and the count is rising by the day,' said Roy. "Initially, an auto carried three passengers. Now, they ferry up to six in violation of traffic rules.'