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

The reported safety problem was motorcycle skidding on the recently painted Chingrighata flyover. The concern became sharper during drizzle and rain, when wet conditions can reduce tyre traction. The flyover includes curves and downward gradients, which may make loss of grip more difficult to manage.

IIT-Kharagpur expert Bhargab Maitra identified inadequate surface friction as a possible risk factor. He also pointed to the flyover’s more-than-13-year-old mastic asphalt layer and multiple coats of paint. The repeated paint layers may have made the surface smoother, potentially reducing the roughness tyres need for grip. Motorcycles are especially vulnerable because they have lower stability and smaller tyre contact areas.

The reported incidents led the West Bengal government to install road studs every 10 metres on the painted stretch. Kolkata Police also said two-wheelers would be prohibited there during rain. However, police and ministers said there was insufficient evidence to prove that painting caused the skidding, and a probe was ordered.

Road-surface friction is the resisting grip between a tyre and the road. It helps a vehicle accelerate, brake, steer and remain stable instead of sliding. A rougher, suitable road surface generally gives tyres more opportunities to grip. When friction is low, a tyre can move across the surface rather than hold its intended path.

On the Chingrighata flyover, IIT-Kharagpur expert Bhargab Maitra identified inadequate surface friction as a possible hazard. He said the more-than-13-year-old mastic asphalt layer may have lost effectiveness. Multiple paint coats may also have smoothened the surface. That combination could reduce the frictional resistance needed for safe vehicle movement, particularly for motorcycles.

The risk becomes more serious when the surface is wet. Drizzle may further compromise traction, while curves and downward gradients demand steady control. Authorities installed road studs at 10-metre intervals and restricted two-wheelers during rain. Still, officials said the evidence did not conclusively prove that paint caused the skidding.

Several features were identified as possible contributors to skidding. The flyover’s mastic asphalt layer is more than 13 years old, and the expert said it may have lost effectiveness in providing frictional resistance. The surface also has multiple layers of paint, which may have reduced its roughness. These concerns matter because tyres need sufficient friction for safe movement.

The flyover’s layout adds further difficulty. It has curves and downward gradients, so riders may need to maintain balance while changing direction or descending. If the surface is already smooth, those movements can become harder. Drizzle may worsen the situation by reducing traction on the painted stretch. The article identifies these as possible contributors, not proven causes.

In response, the government installed rows of road studs at 10-metre intervals on the rainbow-painted section. Authorities also scraped Gariahat Bridge to roughen its surface and improve friction. Police announced a rain-time ban on two-wheelers at Chingrighata, while a probe examines the reported skidding incidents.

Motorcycles are generally more vulnerable when road friction is low because they have lower stability and a smaller tyre contact area. Cars have a broader, four-wheel platform, while a motorcycle depends more directly on the rider maintaining balance and steering control. Reduced grip can therefore affect a motorcycle’s movement more quickly and severely.

The Chingrighata flyover illustrates this concern. Bhargab Maitra said the old mastic asphalt and repeated paint coats may have reduced the surface’s roughness and friction. On a motorcycle, a loss of grip can make it harder to maintain control while negotiating a bend or descending a slope. The problem may become more pronounced during drizzle, when wet conditions further compromise traction.

This vulnerability does not prove that paint caused the reported crashes. Kolkata Police Commissioner Ajay Kumar Nanda and Minister Agnimitra Paul said the cause had not been conclusively established. As a precaution, authorities installed road studs, and police said two-wheeler movement would be prohibited on the flyover during rain.

Curves, downward slopes and drizzle can combine to raise a vehicle’s skidding risk when surface friction is already reduced. A curve requires the vehicle to change direction, while a downward slope affects movement downhill. Drizzle can make the road wet and further reduce tyre traction. With less friction available, the vehicle may not follow the rider’s or driver’s intended path.

At Chingrighata, the expert linked the concern to an ageing mastic asphalt layer, multiple paint coats, curves and downward gradients. He said repeated paint could have smoothened the surface. For a motorcycle, losing grip during a bend or descent can make balance and steering difficult. The combined conditions may therefore increase the challenge of maintaining control, without proving that paint caused any particular incident.

Authorities responded with road studs placed every 10 metres on the painted stretch. Kolkata Police also announced that two-wheelers would be prohibited during rain. The government ordered a probe, while officials maintained that the cause of the reported skidding incidents remained unconfirmed.

Rows of road studs were installed at intervals of 10 metres on the rainbow-painted stretch of Chingrighata flyover. The measure followed reports of motorcycles skidding on the recently painted surface. The studs were one immediate response to concerns about inadequate friction and rider control, particularly during wet weather.

Authorities also took a separate surface-treatment step at Gariahat Bridge. They scraped the bridge surface to roughen it and improve friction. These actions reflect the concern that a smoother road surface may provide less tyre grip. The article also reports that Kolkata Police Commissioner Ajay Kumar Nanda announced a precautionary prohibition on two-wheeler movement on Chingrighata flyover during rain.

The measures do not settle the cause of the incidents. Nanda and Urban Development and Municipal Affairs Minister Agnimitra Paul said there was insufficient evidence to establish that painting caused the accidents. West Bengal Chief Minister Suvendu Adhikari ordered a probe, while the administration continued examining the safety of the beautification work.

Paint on a motorable road must help preserve safe tyre grip because vehicles depend on surface friction for movement and control. Decorative or house paint is usually judged mainly by appearance, coverage and finish. A glossy finish may look attractive but can be unsuitable if it smoothens a surface used by moving vehicles, especially when wet.

That concern is central to the Chingrighata controversy. Bhargab Maitra said multiple paint coats may have reduced surface roughness and potentially affected tyre grip. Congress leader Ashutosh Chatterjee argued that glossy paints should not be used indiscriminately on carriageways. CPI(M) leader Partha Pratim Biswas similarly questioned glossy materials on surfaces used by motorists and bikers.

The administration said anti-skid paints had been used, but officials also said the cause of the reported skidding had not been conclusively established. The issue therefore highlights the need to assess road-paint materials for friction and wet-weather performance, rather than appearance alone. The ordered probe is expected to examine the safety implications.