There are a number of differences between what streetcars do and what you mention. The streetcars I'm most familiar with are directly connected to the power gr

There are a number of differences between what streetcars do and what you mention. The streetcars I'm most familiar with are directly connected to the power grid through overhead lines, and are on rails. Cars would need batteries as private cars won't have a pantograph, or fuel. In either case, there are more things that can break in a fleet of smaller vehicles, so maintenance is higher. Cars also use rubber wheels on pavement, rather than steel wheels on rails, so have higher rolling friction. Streetcars can also handle a high density of passengers. This is important for rush hour, when the load is high. A streetcar has about 3x the capacity of a similarly sized bus, which is in turn much higher than passenger vehicles. In turn, as the article points out, streetcars are best when they have dedicated right-of-way, which allows a higher throughput and predictable latency compared to cars, which are more subject to gridlock. Also, the improved capacity feeds back on itself when people build high-density (eg, 5 story buildings instead of single family houses) along streetcar corridors. The more recent streetcars are also better designed for a wide variety of users. For example, some of the ones I know have a platform which is only slightly above the curb level. This makes it easier for a parent pushing a stroller, or someone with difficulties walking, or on a wheelchair, to enter the streetcar unassisted. The same is not true of most cars. Finally, there are some environmental difference. A personal vehicle has the advantage of not sharing space with strangers. It has the disadvantage that you and your 9 friends can't all travel together. And a streetcar is usually a much smoother ride; a friend get nauseous after 10 minutes as a passenger in cars and buses, but not in streetcars. So while what your friend says is true, there are other factors which make it less compelling.