I was thinking Scotrail with its low line speeds and long sections of curved track could do with 100mph RegioSwinger type trains to allow 156s to scrap and a cascade of 158 sets and even a send off of the HST short sets. Reducing journey times would be the key to improving many of Scotland's longer distance journeys despite many other suggestions posted. Would this be something Transport Scotland, or the DfT/GBR would even consider?
So, firstly why do we have tilting trains?
Tilt exists to make increase the permissible speed for the fastest passenger trains. It does this not by changing any infrastructure, but by making the rules on lateral forces going around sharp curves. Passengers don't feel the outward force because the train tilts to compensate, so drinks don't fly off tables and noone gets slammed into the side of the train.
There isn't any infrastructure change required. Pendolinos use active tilt, which means a trackside beacon tells them to tilt at a specific point, but there are passively tilting trains that just swing slowly.
What this means is that you don't need excessive cant (superelevation or one rail being higher than the other). Every curve on the network has this, but some more than others. On a fast line where everything is going at max speed (think HS2) you can have the perfectly optimised superelevation, but on a mixed traffic route that doesn't work. You need lower cant for the freight trains going at lower speeds, and higher cant for the passengers to compensate for their higher speed, and obviously you can't have both at once. Too high cant means excessive forces from freight, too low and passengers get flung around every time you take a corner at high speeds.
Tilt solves this conundrum. Passengers don't experience the excessive forces, and the track doesn't experience excessive forces from freight trains.
So, tilt is very useful on main lines with very fast passenger trains, but that are very curvy and carry a lot of freight. You can eek out another 15mph or so on curves.
In Scotland this is less of an issue, where passenger trains only travel at 100mph max (WCML and ECML aside). You don't need tilt to compensate and eek out an extra 15mph, as it's less of an issue, and as noted above, you'd need a lot of it to gain a few minutes journey time saving.
Passively tilting trains might work, but they're expensive and quite heavy. Active tilt is basically a dead technology in this country, as that's even more expensive and even heavier. Post HS2, it's likely that we'll see a lot of tilt removed and classic trains on the WCML running at normal (not enhanced) speeds.
In Scotland, you'd be introducing a new technology, with new trains, to save very little in journey time. You'd catch up with stoppers quicker, and likely you probably wouldn't really save much in terms of journey time.
You can receive similar savings in journey time with a unit that accelerates more quickly, or removing the few odd severe speed restrictions across bridges or through tunnels, or using an electric unit which is lighter and accelerates faster.
Faster accelerating reduces journey times, but tilt would add to that, I don't see why faster acceleration negates the need for tilt, used together will lead to even better improvements. As for electrification, it is overrated. Many lines simply will not be viable to electrify, and its not like we're running out of fuel.
Yes, together they'd lead to better improvements, but is it worth spending money on tilt to save 5 minutes from Edinburgh to Aberdeen? That's unlikely.
Electrification is a much more efficient power source, and units can be lighter and accelerate faster. Also remember that most tilt units are electric anyway, so you'd struggle to find new tilting diesel units when the time comes to replace the hsts.
Wiring is expensive, but at the end of the day is a much stronger investment to reduce journey times and increase capacity than tilt north of the border.
