First: Trams can, (perhaps counter-intuitively) cut through traffic making making them instantly very attractive to car drivers. This is fully explained here.
Second: The nature of tram economics ( high capex but 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 and therefore prestigious, unlike buses which are perceived as “cheap and cheerful” and therefore of low status generally used by those without a car.
Fourth: The effect of all this, as is borne out by World-Wide experience* is that people will actually get out of their cars and use trams, (high prestige, faster, comfortable, reliable, frequent) Since trams are about 90 times more effective in terms of using road this space, this creates road space for trams AND buses, which doesn’t happen with buses alone, who are predominantly used by those who don’t have cars.
*(A US Transportation Research Board analysis {US Transportation Research Board TRB Report No. 1221) of 40 years of data of buses replacing rail, and latterly rail replacing buses (as in Houston), showed that light rail (trams) carried 40% more trips than a like for like bus service, and that the majority of this difference was car commuters switching to rail. 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.)
Fifth: Parents will not trust their children to buses to get them to school because they are infrequent and unreliable – diesel buses often breakdown, 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 becuase they are reliable and frequent.
Sixth: Because trams have the effect of reducing in-city car useage, rural bus services get a freer ride into town as well. This speeding up of journey time again makes these rural buses more attractive to otherwise car users who will likely use a quicker rural bus service, again reducing car traffic into the city, and speeding the tram.
Alternatively / additionally, rural buses can deliver passengers to peripheral terminal trams stops where they will speed into town faster than had they been in a car, or queued using the old traffic hindered bus.
This all means a better, cheaper and financially more secure rural bus service. And this feeds back to less in town traffic.
Seventh: Car drivers are discouraged from using Park and Rides because they have to first deviate to the Park and Ride, then wait for a bus, then queue to get onto a slowly boarding single entry bus. The bus then re-joins the traffic jam, so the Park and Ride takes longer than simply staying in their car in the traffic queue.
On the other hand, trams from the P&R are
a) more frequent
b) quicker to board due to multi-door boarding and off-tram ticketing – it’s just turn up and go. For the reasons previously cited the tram will get them to their destination quicker than the bus ( or remaining in their car in the traffic ) would have. Furthermore, the tram with its rapid boarding, stopping in the road, and greater length can pick up passengers en route without significantly compromising its journey time.
Eighth: The original Bath trams had a thriving business shipping parcels, ladders, timber, even lunches around Bath using a network of local shops as mini-depots and reception points.
Rather than build a Freight Consolidation Depot, which is expensive and ugly, it is perfectly possible for many of the HGVs to simply stop at the park and rides or peripheral tram stops (11 in number) located around the city and to tranship the wheeled baskets of goods that most of the HGVs carry to off-peak trams or special freight trams.
These baskets can then be dropped of at locations around the city and wheeled by specially employed Freight Captains to their destination. All checked and secured with electronic tagging. This will greatly reduce the ingress of large HGVs which generally are carrying these wheeled baskets and which are dropped off typically at up to 5 different locations. The time saving accruing to the HGV company will easilly pay for the cost of the freight captains. Again removing HGVs will generally speed entry of other vehicles into the city.