SCADA Software for Speed Control in Trains?

In trains in particular or in railway control systems as a wider remit?

In the UK, HM Railways Inspectorate will not permit software to be used for train signalling and routing, unless that software is backed-up by hard-wired electrical interlocks that inhibit conflicting movements, on safety grounds. If the two systems agree, then the movement happens. If they don't, then it doesn't. It all goes back to a piece of legislation called the Regulation of the Railways Act 1889 (the "Lock", "Block" and "Brake" Act). That act has been fundamental to ensuring a high level of safety on the nation's railways. The principles enshrined within it are still applied today, even on modern 'metro' systems.