(its worth noting that trams only work where there is a high demand for passengers, which means cities or between cities, and that as such, they have a capacity 3 – 5 times that of a bus service on the same route.  See: https://bathtrams.uk/relative-carrying-capacity-cars-buses-trams/ Buses are great for low demand city routes and for rural areas)

First: Trams can, (perhaps counter-intuitively) cut through traffic making making them instantly very attractive to car drivers due to “Green Wave Traffic Light Preemption” . This is fully explained here.

Second: The nature of tram economics ( high capex,  low opex) means trams are more frequent – every 6 minutes so its just turn up and go – and this of itself reduces journey time; also no annoying hanging around and getting there early to make sure you don’t miss it, or nagging worry you have missed it.

Third: Trams are experienced as solid, expensive, more comfortable, quieter, and less jerky than a bus, and prestigious, unlike buses which are perceived as “cheap and cheerful” and therefore of low status and  generally used by those without a car. .

Fourth: Because a tram is a rail vehicle, and constructed completely differently to a road vehicle, it has much more space inside meaning people are not crammed together in multiple bench seats, and this is very attractive, as parents will not want their children trapped next to a stranger ditto you women.

Fifth: Again because of their different construction, trams can have large multiple doors and this means boarding and alighting can be much more rapid in even a 250 seat tram, than a 70 seat bus, thus making for quicker journey times.

Fourth: the effect of all this, as world-wide experience bears out,* is that people will actually get out of their cars and use trams — faster, more comfortable, more reliable, more frequent, and carrying a prestige that buses do not. And because a tram moves far more people for each vehicle movement, it frees road space rather than consuming it.

The arithmetic on Gloucester Road makes the point. The corridor currently carries around 900 cars and 35 buses in the peak hour; at observed loadings of roughly fifty passengers a bus, those 35 buses move about 1,750 people. Ten trams an hour on the same street deliver 2,500 passengers per hour per direction — more people, in under a third of the vehicle movements. That released road space benefits everything else using the street, buses included, which is not what happens when the answer is simply more buses.

There is a second effect. Tram passengers are markedly less likely than bus passengers to be travelling because they have no alternative: only about 11% of tram passengers use a concessionary pass, against 35% on buses. A tram is chosen; a bus is too often the only option available.

*The US Transportation Research Board, Report No. 1221, analysed forty years of American data on rail services converted to buses and, latterly, buses converted to rail. Its finding is a controlled comparison: where travel time, fare, frequency, population and density are held equal, rail transit attracts between 34% and 43% more riders than an equivalent bus service. The report states that its data do not explain why, but points to the clearly identifiable route, delineated and often protected stops, more comfortable vehicles, freedom from fumes and noise, and more generous vehicle dimensions. Passenger behaviour is a stronger signal of travel preference than attitude surveys.

(Note This means that those who still wish to or must drive find it less inconvenient, because many of the previous car drivers will now be in the tram.)

Seventh: Parents will not trust their children to buses to get them to school because they are infrequent and unreliable – diesel buses often break down, there are driver shortages due to the stress of bus driving, and buses are delayed by traffic.  This is a key driver of the parents school run which is a major part of Bath’s traffic congestion.   In tram towns people will happily permit their children to use trams even if a tram change is involved because they are reliable and frequent.

Eighth: becsue trams are a heavy rail vehicle they are smoother and quiteter, unlike a rattley jerky bus which are very uncomfortable due to vibration, and the banging and rattleing and jerking as a bumpy road is encountered and all the stop starting and swerving that a bus encounters.

Ninth: There is also a subtle psychological effect, in that being in a bus is akin to having a lift in a strangers’ car, and subconsciously passengers are paying attention to and worrying about “driving the car” as it negotiates the traffic, traffic lights etc.

In a tram the user is completely isolated, has no ability to drive the tram and doesn’t need to subconsciously worry about at it, as the tram is like a train in its own isolated environment.  Thus tram travel is far less anxiety making than a bus journey.