An IIT-Kharagpur road-safety expert has identified ageing asphalt, multiple layers of paint, road curvature and inadequate surface friction as factors behind motorcycle skids on Kolkata’s rainbow-painted Chingrighata flyover, prompting authorities to remove the paint and tighten speed controls.
Police said the flyover would no longer be managed only through rain-time restrictions on two-wheelers. The focus is shifting to reducing motorcycle speeds throughout the day, with a 40-kmph limit recommended after an inspection by Bhargab Maitra, an IIT-Kharagpur expert in road safety and transportation.
Maitra said the flyover’s mastic asphalt layer was more than 13 years old and had lost effectiveness in providing the required frictional resistance. Multiple layers of paint had further reduced the roughness of the surface, he said. “With every layer, brightness has improved but friction has been compromised,” Maitra observed.
The risk is greater for two-wheelers because motorcycles have lower stability and a smaller tyre contact area, according to the expert. The flyover’s downward gradients and curves can further increase the possibility of riders losing control, particularly during drizzle.
The assessment followed viral videos showing motorcycles skidding on the freshly painted surface. The videos also drew bikers seeking to film reels on the colourful stretch, leading police to deploy civic volunteers to discourage riders from stopping, slowing abruptly or recording videos while crossing the flyover.
Police regulated two-wheelers through advisories during the latest inspection period rather than imposing a complete ban. An officer said motorcycles would continue to be stopped completely during rain, while speed restrictions would be strengthened in normal conditions. “We have put up signage and are regulating bikes. Following the inspection by the IIT expert and corrective work by KMDA, we are allowing motorcycles, although the advisory remains,” the officer said.
A Lalbazar officer said police would reduce the maximum permissible speed and stagger traffic entering the flyover to minimise speeding. “Since the exact reason behind the accidents is not clear, we are not taking chances, particularly near the curve,” the officer said.
The Kolkata Metropolitan Development Authority has begun manual and mechanised removal of paint from the flyover to restore surface roughness. Maitra recommended replacing the ageing mastic layer, installing speed cameras to enforce the 40-kmph limit and conducting safety audits of all city flyovers every six months.
The investigation has been complicated by the fact that none of the riders involved in Wednesday’s viral skidding incidents reported the incidents to police. Authorities therefore do not have accident-specific complaints from those cases. Environmental activist SM Ghosh and other citizens have also sought written clarification from the paint manufacturers on whether the coating was road-grade thermoplastic material and whether the prescribed application standards were followed.
For now, police restrictions, traffic staggering, paint removal and the rain-time stoppage of two-wheelers remain the stated safety measures. The next steps are the completion of corrective work by KMDA, enforcement of the recommended speed limit and consideration of the proposed flyover safety audits and speed-camera system.
