Bengaluru: Why do roads in Bengaluru develop potholes after just one spell of heavy rainfall? That’s because the Bruhath Bengaluru Mahanagara Palike (BBMP) uses unscientific methods to build roads, say urban transport experts.

M N Sreehari, an urban traffic expert, says: “Flash floods, cyclones or snowfalls are common across the globe, but they do not create potholes because roads there are built scientifically. When there are no potholes, there are few accidents. Developed countries also follow a proper mechanism to repair a damaged road.”

Sreehari says the BBMP must have proper guidelines for road construction. “Building asphalt roads requires heating a mixture of sand, gravel and bitumen to 140ºC. Bitumen should be 5.5% of the mixture. But most of the time, it’s just 3.3%. When the mixture is brought to the construction site, it should be heated to 120ºC. This heating requirement is not met either. The third flaw is that road builders add soil, not sand, to the mixture because sand is not cheap. Because of this flawed process, the mixture does not hold to the ground, which leads to potholes when it rains,” Sreehari added.

Lokesh Hebbani, a city planning expert, suggests white-topping or concretising of roads to make them durable and avert accidents. “The government spends thousands of crores on asphalting roads which get damaged within a year. It would be better if the government spends the same amount on white-topping roads,” he said.