A car does Frankfurt to Saarbrücken in roughly 1h 57 over 180 km. The motorway runs almost where the map does — 180 km of road across 155 km of straight line. The difference from every other way of making the trip is that it starts at your address and ends at theirs.
The fare is fixed when you book, so a closed lane or a slow stretch costs you time and not money — there is no meter and no waiting charge. Pickup is any address in Frankfurt: a home, a hotel, an office, a venue. Drop-off is the exact address in Saarbrücken, not the nearest station to it. The route crosses from Hessen into Saarland; the price covers the whole of it including tolls. The same fixed-price arrangement covers Frankfurt to Strasbourg, a separate route with its own measured distance.
An executive saloon on a 1h 57 run is a quiet place to work: the same car the whole way, no changes, no platform, and a driver who takes the route. Longer bookings are usually made a day or more ahead, and the return leg can be fixed at the same time and the same price. Arriving by air instead? Frankfurt Airport Transfers covers every destination we serve from the airport.
The two journeys a rail ticket does not include
A train time is measured Hauptbahnhof to Hauptbahnhof, and almost nobody starts or finishes at one. The real Frankfurt–Saarbrücken journey by rail is usually three journeys: getting to the station with your bags, the train itself, and getting from the far station to the actual address — the last of which is a taxi at the far end, at a metered price, in a city you may not know. Those two legs are where the published time and the published fare both stop being the whole story. A private car removes them by starting and ending at the addresses instead, which is why the comparison is closer than a timetable makes it look.