The document discusses the challenges internal combustion engine (ICE) vehicles face in meeting CO2 emissions targets by 2050. It notes that while the number of vehicles worldwide is expected to increase to 3 billion by 2050 from 750 million in 2009, ICEs have limitations as gasoline combustion is difficult to make lean and diesels are expensive to build and require expensive exhaust treatment. It also outlines CO2 legislation targets and costs associated with different solutions, suggesting optimized ICEs could meet targets at the lowest cost compared to hybrid, plug-in hybrid, and electric vehicles. The document advocates for diverging ICE technologies between on- and off-highway applications to balance these challenges.