Final answer:
The roadway system, used mostly by personal vehicles, is the workhorse of the U.S. transportation system and accounts for about 28.2 percent of transportation-related emissions. This system is not good for long-distance travel or sustainable due to environmental concerns.
Step-by-step explanation:
Understanding the U.S. Transportation System
The workhorse of the U.S. transportation system is still the roadway system, predominantly used by passenger cars, light-duty trucks, sport utility vehicles, and minivans. This type of travel accounts for a significant portion of transportation-related emissions, with more than one-quarter - 28.2 percent - of such emissions resulting from the consumption of fossil fuels for transportation. Roadways are crucial for the efficient movement of goods and people and have traditionally been a central part of urban planning and community development.
However, this type of travel is not good for everything. It is not particularly efficient for long-distance travel compared to air or rail transportation, nor is it sustainable given environmental concerns, highlighted by the problems raised by environmental activists such as emissions contributing to climate change.