Kolkata’s Chingrighata flyover is facing road-safety concerns after IIT-Kharagpur road-safety and transportation expert Bhargab Maitra identified reduced surface friction as a possible risk factor for motorcycles on its recently painted stretch.
According to multiple reports, Maitra inspected the flyover and identified several factors that could make the surface hazardous, particularly for two-wheelers. These include a mastic asphalt layer that is more than 13 years old, multiple layers of paint, the flyover’s curves and downward gradients, and inadequate surface friction.
Maitra reportedly said the ageing mastic asphalt layer had lost its effectiveness in providing the frictional resistance required for safe vehicle movement. Repeated coats of paint may have further reduced the road surface’s roughness, potentially affecting tyre grip.
Maitra also reportedly said the flyover’s mastic asphalt surface, which is over 13 years old, may no longer provide adequate friction. He added that repeated coats of paint had further smoothened the surface, improving its appearance but potentially reducing the grip needed for safe vehicle movement.
According to the expert, motorcycles are more vulnerable to reduced surface friction because they have lower stability and a smaller tyre contact area. A loss of grip can make it harder for riders to maintain control, particularly while negotiating bends or descending sloping sections.
The risk could increase during drizzle, when wet road conditions may further compromise tyre traction. The combination of reduced surface friction, curves and downward gradients could make it more difficult for motorcyclists to maintain balance and control on the flyover.
Maitra’s assessment highlights the potential road-safety risks posed by the condition of the underlying asphalt, multiple paint layers and the flyover’s design, particularly for two-wheeler riders. However, these factors alone do not conclusively establish that the paint caused the reported skidding incidents.
Following the reported incidents, the West Bengal government installed rows of cat’s-eye road studs at intervals of 10 metres on the rainbow-painted stretch of Chingrighata flyover. Authorities also roughened the surface of Gariahat Bridge by scraping it to improve friction.
Kolkata Police Commissioner Ajay Kumar Nanda said two-wheeler movement on the Chingrighata flyover would be prohibited during rain as a precautionary measure. He also said there was insufficient evidence to establish that the reported accidents had occurred because of the painting.
Nanda said experts involved in the painting work had informed the police that the paint used had anti-skid properties. He also cited possible contributing factors such as rider negligence, excessive speed and the flyover’s sharp bend.
Urban Development and Municipal Affairs Minister Agnimitra Paul similarly said the administration had not conclusively established the cause of the skidding incidents.
