Kolkata's rainbow-painted Chingrighata flyover raises road safety concerns: What an IIT expert says about skidding risks

Kolkata’s Chingrighata flyover is facing road safety concerns after IIT-Kharagpur road and traffic safety 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 unsafe, especially for two-wheelers. These include a layer of cast asphalt that is more than 13 years old, multiple layers of paint, flyover curves and declining grades, and insufficient surface friction.

Maitra reportedly said that the aging cast asphalt layer has lost its effectiveness in providing the frictional resistance needed for safe vehicle movement. Repeated layers of paint could further reduce the roughness of the road surface and potentially affect tire grip.

Maitra also reportedly said that the flyover’s cast asphalt surface, which is more than 13 years old, may no longer provide enough friction. He added that repeated coats of paint further smoothed the surface, improving its appearance but potentially reducing the grip needed to safely move the vehicle.

Why are two-wheelers more vulnerable?

According to the expert, motorcycles are more susceptible to reduced surface friction because they have less stability and a smaller tire contact area. Loss of grip can make it difficult for riders to maintain control, especially when cornering or going down banked sections.

The risk can increase during drizzle, when wet roads can further degrade tire traction. The combination of reduced surface friction, turns and dips could make it more difficult for motorcyclists to maintain balance and control on the overpass.

Maitra’s assessment highlights the potential road safety risks posed by the condition of the underlying asphalt, multiple layers of paint and the design of the flyover, particularly for two-wheeler riders. However, these factors alone do not conclusively prove that the paint caused the reported skid events.

What steps have the authorities taken?

Following the reported incidents, the West Bengal government installed rows of cat’s-eye road bollards at 10-metre intervals on the rainbow-painted section of the Chingrighata flyover. Authorities have also roughened the surface of the Gariahat Bridge by scraping it to improve friction.

Kolkata Police Commissioner Ajay Kumar Nanda said the movement of two-wheelers on the Chingrighata flyover will be prohibited during rains as a precautionary measure. He also said there was insufficient evidence to show that the reported accidents were caused by the painting.

Nanda said the experts involved in the painting work informed the police that the paint used had anti-slip properties. He also cited possible contributing factors such as driver carelessness, excessive speed and the sharp curve of the overpass.

Urban and Municipal Development Minister Agnimitra Paul similarly said the administration has not conclusively established the cause of the skidding incidents.