Complex sentence: However, Transportation Research Board studies show greater safety disparities among vehicles of differing price, country of origin, and quality than among vehicles of different size and weight Other researchers also dispute the incompatibility of reduction in vehicle weight and increased fuel economy.
Split into simpler sentences: However, Transportation Research Board studies show safety disparities may exist among vehicles of differing price, country of origin, and quality not just among vehicles of different size and weight alone. Some other researchers dispute the incompatibility of reduction in vehicle weight and increased fuel economy.