That little bugger has made its appearance at AutoPuzzles before.
It does help when you know where to look - still not that easy to find, though.
So to recap, we start from Rust 4, the Chausson bus, built in the outskirts of Paris. Then it's Hint 22:
22: In this town you have to enter metro line 13 and leave it at the 12th station. The station's name will give you the customers of the next car
The nearest metro station to the main Chausson factories is Asnières - Gennevilliers - Les Courtilles on Line 13. Ride for 12 stations and you arrive at Invalides, indicating that invalids or disabled people would be the customers of the next car.
That's Rust 6, a Salamander invalid car, based on a modified Reliant Kitten chassis, and powered by an 1100 cc Ford engine. This was commissioned by the Social Services Department of a British city (I won't say which
) as a replacement for the Invacar vehicles. It was produced from 1981 to 1984, by which time specialist disabled vehicles had been made obsolete by the British "Motability" scheme, which aimed to provide standard production cars modified for use by disabled drivers.