BENGALURU: The recent rains have brought some cheer for Bengalureans, as there has been an increase in the ground water table and lakes are brimming. But on the flip side, the city’s roads have been battered and vehicle users struggle to negotiate the potholes.
The situation worsens with every heavy downpour. The roads get waterlogged and many vehicles get stuck in the water. The Bruhat Bengaluru Mahanagara Palike (BBMP) blames the heavy rain for the bad state of roads, but the fact is that it is not about the monsoon, it is about how the roads are made.
How is it that about 100 days of rain can leave the city’s roads in such pathetic shape? In some other countries which receive more rainfall than India, their roads are better maintained compared to Bengaluru.
The problem
The city’s roads are mostly bituminous (black-topped). The bitumen roads exhibit a simple chemical property called stripping of bitumen when they are in sustained contact with water. In normal situation, it constitutes of stone aggregate, surrounded by bitumen, which acts as a binder and keeps the road intact and elastic.
When there is a rainfall, water settles on the road and remains in contact with the road surface for a longer time due to absence of cross slope on most of the roads. At this juncture, the bitumen strips off from the stone aggregate resulting in loss of its binding property. Due to this, the aggregate becomes loose and this leads to a formation of a pothole.
Roads should be supported by simple cross slopes, which is technically called ‘camber.’ When there is a rainfall, these cross slopes help in draining out the water.
In addition, roads suffer from poor maintainence and poor quality of construction which add to the woes of the road users. The re-laying of roads and filling up of potholes should be governed by the Indian Roads Congress (IRC) codes. These guidelines prescribe methods to fix potholes scientifically. It will result in good quality roads which do not require any interference for at least five years.
Needless to say, the associated economic cost of potholes is manifold and enormous in terms of increase in travel time and thus decrease in overall productivity of the city, more air pollution due to dust particles, health impact due to exposure to dust and jerks to backbone/human body due to vehicles bumping over potholes.
(The writer is an Associate Professor, Transportation Engineering, Department of Civil Engineering, IISc)