According to an research by IFPRI (International Food Policy Research Institute):
For every million rupees spent, roads raised 335 people above the poverty line, and R&D 323. Every million rupees spent on education reduced poverty by 109 people, and on irrigation by 67 people. The lowest returns came from subsidies that are the most popular with politicians – subsidies on credit (42 people), power (27 people) and fertilisers (24 people).
Swami has recently published a very good article on how roads can be one of the most effective way for poverty elevation.
Connectivity enhances the value of every other rural investment, since it empowers people through improved mobility and access. People can more easily buy agricultural inputs and sell their produce. Children can go more easily to schools, cattle can more easily get veterinary help, and the sick can get to health centres. Remote areas have, by definition, the worst connectivity. They are among the poorest and slowest-growing, but accelerate when given connectivity.
Roads can incubate a thousand small businesses, and can convert villages into towns. Government staff are much more willing to be posted to places with good connectivity, so roads improve administration. Rural productivity cannot be high without roads, but can be very high with them.
No wonder even in America the railroad boom came first and then came the rapid growth and development.
When will Indians understand it 
