Self-driving cars, taxis and buses could pose a threat to the viability of commuter trains and subways, according to a study by the Boston Consulting Group.
Nicholas Lang of BCG estimates between a third to to half of rail passengers could migrate to self-driving transportation by the year 2040.
One example of how this could happen: imagine automated mini-buses that seat up to 15 people. Lang thinks they could be more comfortable, convenient and cheaper than existing public transportation.
"You don't have a commuter train every 10 or 15 minutes," says Lang, "but you would have an autonomous vehicle almost every minute in a specific neighborhood."
Lang says automated buses have the potential to have much lower fixed costs than passenger rail.
"In that segment of 12-15 people, you have a sweet spot," Lang says. "Buses are big enough to be cost- effective -- and small enough to be relatively flexible in regards to routing."
Lang says passenger rail systems can fight back by reducing costs, and offering start-to-finish transportation packages that get customers from the front door of their house to the front door of their workplace.
Meanwhile, there is one large metro area that currently has no large-scale passenger rail system: Detroit.
The city could be an ideal place to experiment with automated buses, since it wouldn't threat existing infrastructure.