Tourist buses are fundamentally recreational, not a form of transportation. Their goal is to allow their passengers to see specific things, so they often use inefficient routes and move slowly to give their passengers a better view. Most of their passengers ride the bus along a circular path, rather than boarding or disembarking along the way. (Often, they don't even allow boarding after the tour begins.) As such, they place more load on the road network than a city bus, without any of the transport benefits.

Well, being able to see the city is a benefit. It still seems like if they take regular buses (or worse, taxis), it will be more crowded and less efficient.

> It still seems like if they take regular buses (or worse, taxis), it will be more crowded and less efficient.

Those aren't substitutes. Tourists ride tourist buses to be taken on a guided tour, not as a means of getting from one place to another. Passenger buses and taxis don't provide that.

Unless you think tourists will just decide to skip Paris, they are going to substitute some way of getting around the city and seeing at least some of the places they want to see, even if it's an imperfect substitute. A guided tour is one way, exploring on your own with a guidebook is another.

There may be an argument here about induced demand: more capacity results in more tourists until it gets too inconvenient at some higher level of visits, and similarly in reverse. But this suggests that removing capacity will result in bottlenecks due to traffic somewhere else. Things will get worse somehow until the word gets around and people reduce the number of trips they make.

Seems likely that we're missing the crowd control element.

It seems likely that 46 people will be unable to ride the subway or taxis and arrive at a single destination at once.

By blocking busses, onboarding and offboarding will not have the blocking behavior along with the other logistics of driving and parking large vehicles.

To computing terms, it's likely less efficient for the people on the bus (a large blocking operation) though more efficient for parallelized split groups of people and if not directly, then at least in diversity of groups of people.

Many tourist busses have insanely high prices, and as a result end up nearly empty.

In London for example, a hop-on-hop-off bus would cost you £25, while a regular bus would cost you £1.50 for an hour or more of top-deck sightseeing.

Said tourist busses normally only have ~5 passengers on out of a capacity of 60

> what's more environmentally friendly than buses

subway, tramway, bikes, you can event visit a lot of things walking the city, there's no need to have a bus only to go to the city