Here's an interesting quote on the report into the 1999 collision between a class 142 unit and an express passenger train at Winsford.
The railway inspectors say lightweight rail-bus trains do not meet current safety standards and they are concerned that some of them are now being used on the same tracks as conventional heavyweight inter-city and freight trains.
See
http://news.bbc.co.uk/1/hi/uk/383785.stmHave any alterations been made to these units in the 8 years since that collision so that they now meet mainline safety standards?