Having driven the things far too often in CT days, I'd say the 170/1s were the most absolutely awful of a class of awful units.
I'm still not quite sure what work 170s were designed for. They didn't have the acceleration or the braking (full service excepted) for stopping services; they didn't have the capacity for interurban work (and especially not the 3-car 170/1s with that ridiculous "premier class" section in the middle car).
A 3-car 158 had better acceleration, a better range of braking, more seats for the passengers, and back in the days before OTDR could easily top the ton.
What else? Well...
- There was the cab with the drivers' seat which was impossible to get comfortable, and which had to be folded over to allow you to move around the cab.
- Self-setting DRA on the 170/1s, which might have been a great idea on an Intercity route, but on stopping services with fixed distants and warning boards everywhere, not so great.
- Cab aircon which would require resetting (which involved dropping the roof panels) at least three times between Nottingham and Birmingham.
- Power... Open the throttle, wait five seconds until it decided whether or not it was going to respond. Even if it did, you didn't get full power until 10mph regardless of the power notch selected, and try that game when you're stopping every 2 or 3 minutes and don't have enough time in the schedule even on full power.
- Did I mention the braking? Every stop with a 170 was "interesting", because the braking was never quite the same twice. 153s do that, too, but generally it's only brake release where they play games; on 170s it was brake applications which you could never quite trust. The only good thing about 170 brakes was that in full service they'd seemingly stop in a platform length, but the whole train would be thrown over in the process.
And so on.
I absolutely detested the 170s
(does it show?), and especially the 170/1s when NatX decided to dump them onto CT once MML had no further use for them.
If a 15x turned up in place of a 170, a CT driver would always breathe a sigh of relief. More comfortable, more responsive, more predictable, and just as able to keep time on CT's schedules.
The best all-round DMU is the 156. Simple, robust and they just seem to keep on going. Just a shame they never seem to have working saloon heating any more.