........But I think you're missing something (not that I've ever seen a simulator). While road speed limits are set at particular speeds for a variety of political reasons with safety in mind, rail limits are much more closely tied into the design and maintenance of the p'way (and to some extent the capabilities of certain stock, particularly its breaking abilities). I don't expect computer simulators have built in the variables for movement in the railhead under the varying vertical and lateral pressures from a few hundred tons bearing on them at changing vectors. In fact I'd guess that computer simulators don't simulate anything to do with the track at all, and treat it as if its just a route through a 2 dimensional space. Or am I underestimating them?
Definitely underestimating !
For gauging purposes the programme assesses the movement of the vehicle taking into account tolerances for wheel wear, loading, and deflection on the suspension, and associates that with variations in the tolerance of the track both up to and slighty above the maintenance "intervention level". In this way we can assess the picture of the swept envelope relative to line side structures.
When we do a track renewal our design also looks at a number of these elements.
Maximum speed of atrain therefore is more related to the risk of the vehicles striking another train or a lineside structure such as a platform rather than becoming derailed.
There is quite a considerable tolerance before that becomes a realistic risk, although the ride quality at that stage will be like Alton Towers.
One thing that many Drivers fail to understand is that with modern S&C we can give a very smooth ride through the S&C on the diversionary routes, and this leads Drivers to running at ever higher speeds. The problem is that this leads to excessive wear on the switches which then fail much quicker than they should.
This was a particular problem for us at Doncaster South Yorkshire Jct when we raised the line speed slightly and then found that Drivers were pushing even this higher speed. As a result we were experiencing incredible fast wear on the switch rails.
As a result we had to bring the speed guns out and capture a few.
Issues such as this cannot be seen by Drivers but they do have a marked effect on the quality and lifespan of the track and its components.
Track technology is now in the computer age and is no longer something that we can "eye in". Those of us who take a pride in the job talk about longitudinal variations measured in mm over maybe a 1000m and the track monitoring trains now measure very accurately how the track is performing or not.
We can now "see" a section of new track deteriorating and can now intervene to carry out remedial work whilst it is still under our care, and we have the site planned for potential follow up snag works.
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