Indians are rushing headlong to get behind the wheel, as incomes rise, car loans proliferate and the auto industry churns out low-cost cars to nudge them off their motorcycles. They bought 1.5 million cars last year, and by some estimates India is expected to pass China this year as the fastest-growing car market. That car mania was on display at the Auto Expo in New Delhi this week, as Maruti Suzuki unveiled a concept car.