Haryana has an installed capacity of around 4.8 million vehicles (1.2 million for Maruti and 3.6 million for Hero Honda).
Harley Davidson is also setting up an assembly unit at Bawal in Haryana, which will become operational by the first half of 2011.
However, the company has not yet furnished details on its investment or production plans.
Maruti will produce 1.2 million cars from its facilities at Gurgaon and Manesar.
Besides, it has plans to add two more plants at its Manesar unit to increase capacity by 0.5 million by 2013.
The total investment in both plants is Rs 3,625 crore.
Hero Honda, which is the largest producer of motorcycles in the world, has two plants in Haryana: at Gurgaon and Rewari.
It produces 6,000 units a day at each.