Earth's vehicle population on track to top 1B by 2020, possibly earlier

25% spurt from present total of about 800M seen as challenge, but also opportunity

Challenges include increasing city traffic congestion, greenhouse emissions

Industry not stagnant, says GM's Paul Ballew, but growth managing strategy needed

Trends toward car count of at least 1B spur development of more efficient fuel

Congestion in metro locales like London led to tax on cars entering city center

New York also facing serious problem over lost productivity due to huge traffic tieups

Toyota scores big w/ Prius hybrid; Ford now cutting back of gas-guzzler SUVs

"For us in the industry, the next 10 years will be fascinating." -- Paul Ballew, executive director of market and industry analysis, General Motors Corp

If one-third of SUVs were driven by diesel engines, you could save the imports from Saudi Arabia in total." -- Herbert Kohler, chief environmental officer, DaimlerChrysler