This is a reason why buses are not as cheap as they seem at first glance.
Often times, buses are favored because they require low capex (adding lines is easy, politically palatable, etc).
But in practice, on really busy bus lines with high throughput, it shreds the roads, to the point where you really need to re-pave the whole road every 10 years -- in which case, why not just put a rail line in and use a train!
That is similar to the reason trackless trams are not economically viable. They are essentially just busses that are guided, but because of their precision the cause really bad erosion on the parts of the road where they drive. At least with busses there is variability on the parts of the road that are eroded and it affects the whole road more evenly
There are certain places/conditions where trackless does make more sense, however. Philadelphia still has several trolleybus lines active for instance, in addition to buses, trolleys, subway, el-train, and traditional rail.
My guess is that it works here because our roads turn to shit anyhow from the freeze/thaw cycle, so it's not adding as much maintenance burden as it would elsewhere.
Assuming you don't have the ability to separate traffic, you don't really gain anything. Cars have to be able to drive in the same lane, so the tracks have to be level with the roadbed and asphalt gets torn up very quickly along the tracks.
In the mid-90s, Seattle started excavating its bus-stops-on-a-slope and pouring a new concrete foundation, because the busses were warping the asphalt so badly.
I was just back there this last weekend, and you can no longer see any of the concrete - it has all been coated with asphalt. However, I assume its a rather thin layer because none of the bus stops I checked show the signs of damage that were becoming common in 90-96.
They opened a new truck stop near me with asphalt roads. 6 months later they tore it up for concrete because the asphalt shifted into lumps where the trucks were turning cono
Asphalt, like glass, is an amorphous solid. When a heavy truck sits still on asphalt, asphalt will flow out from under the tires. Not only do you get a depression and eventually a pot hole where the tire was, and you get a little hill next to it.
You just about need an offroad vehicle to avoid hitting the street.
Moreover, when a heavy vehicle like a loaded passenger bus has to accelerate from stationary on a hill, it exerts incredible force on the asphalt below it.
Doesn’t just happen on hills you can see this phenomenom on flat intersections too that have seen a lot of nearby construction vehicles (cement trucks, dump trucks, etc are probably the worst).
Maybe the fact that every car in the US weighs two to three times more as it needs doesn't help either. I'd be curious to get the numbers to see what's worse. A half packed bus every 15 minutes or thousand of pickup trucks.
https://www.kgw.com/article/news/verify/yes-bus-more-road-da...