This paper focuses on the effectiveness of helmets in reducing fatality and serious head injury for motorised two-wheeler riders. Field data from the Road Accident Sampling System – India crash database on 1,197 motorised two-wheeler crashes was used to analyse the crash and injury pattern, helmet type and helmet damage. The analyses were performed using weighted and unweighted data. The results show that helmets are 24% effective in reducing the risk of fatality and 10% effective in reducing the risk of serious/fatal injury. Injury analysis shows that an unhelmeted rider is approximately 1.5 times more likely to sustain an Abbreviated Injury Scale, AIS 3+ head injury compared to a helmeted rider (51% unhelmeted against 33% helmeted). AIS 3+ thoracic injuries were seen in case of both unhelmeted and helmeted riders (19% and 25% respectively). In addition, AIS 2 injuries were found more commonly to the lower extremities in case of both unhelmeted (23%) and helmeted (26%) riders. Detailed injury analysis of helmeted riders with AIS 3+ head injury shows that helmets are 35% effective in reducing the risk of AIS 3+ head injuries. Investigation of helmeted riders with AIS 3+ head injuries show that majority of these riders had collided with heavy vehicles (55%) or fixed objects (40%). This is significantly different from the vehicle mix and crash conditions seen in developed countries. Consideration of vehicle compatibility for helmet design and crash avoidance through technology and infrastructure are proposed.