This series thus far has discussed all modes together. In this and the next column, however, we’ll look at each of the basic modes of public transport, beginning with buses.

1. Rudolph Diesel’s invention: While bus transportation began in the 19th century, the diesel engine’s impact was really made in the past century.

2. Trackless trolleys: Few streetcar networks in the U.S. were ever profitable for long, despite significant investment. Operators were constantly looking for ways to reverse this, and the application of electric traction to buses helped to ease financial pressures, allow cross-subsidization of electric utilities looking for new power markets and led to the conversion — for better or worse — of most rail-based systems to rubber-tired ones.

3. Purpose-built buses: In the early years, buses were mere adaptations of other types of vehicles, such as horse-drawn carriages. The White Motor Bus Co. and Frank Fageol’s Safety Coach, among other developments, pushed these designs much further until they became the purpose-built integral bus-chassis designs of today.

4. National City Lines: True, the owners of this company, which included oil, rubber and auto companies, were convicted of engineering a conspiracy to undermine competition to their real businesses. However, as has been pointed out so many times in this series, other factors also helped their cause.

5. Rise and fall of Trailways and Greyhound: With the huge investment in roads came coach services offering consumers a choice over more expensive rail, particularly for poorer and disadvantaged Americans. They also allowed millions to see America and stay connected to loved ones by “leaving the driving to us,” in the words of Greyhound. Intensive competition from the private auto and, later, the airline industry cut heavily into the intercity coach’s market share. Deregulation of the bus industry further shifted the motorcoach industry’s business mix to the point where less than 10% is linehaul today.

6. The civil rights movement: We would be amiss if we did not recognize the critical venue the bus industry became during African Americans’ struggle for equality in the 1950s and 1960s with the Montgomery bus boycott, Rosa Parks’ refusal to take a back seat and the marches that used buses to mobilize. If there were any doubts that discussions about whether public transportation has an impact on access and mobility for all Americans, remembering why the boycotters and the freedom marchers took action should answer the skeptics.

7. Whither intermodalism: Congress enacted this commitment in 1991, but coordination of information, physical interconnections and fare cooperation among all modes remain inadequate.

8. Challenges from abroad: Beginning in the 1970s, new competitors began to offer America’s cities new choices in bus lengths and technologies, encouraged by some officials who foolishly predicted that the decade’s oil shocks would lead to an annual market of 10,000 transit buses. Domestic suppliers demanded Buy America protection to save U.S. jobs, but the two decades since such laws have been enacted have produced a mixture of success and unfulfilled hopes — on both sides of the debate.

9. Technology explosion: Partly related to the previous item, the U.S. transit industry enjoys an unprecedented range of choices, but also an equally unparalleled matrix of supplier headaches. The industry has enjoyed record levels of investment — and perhaps an equally high number of unhealthy companies. Why?

10. Bus rapid transit: Most of the elements of this new mode are not new, as busways and exclusive bus lanes have been around for decades. So have signal priority systems. But applying other techniques mainly used in rail modes, such as stations with level boarding, prepaid fares and faster route structures, is relatively new to buses. The result will be a revolution in how cities view bus transport. Will buses rescue rail — again?