Conversion of Manchester Metrolink to low-floor operation?

[61653 HTAFC]

Tram-trains don't meet the heavy rail standards for crashworthiness - that's the reason they need enhanced train protection provision such as TPWS at all signals. The degree of risk depends on the probability as well as the severity of a possible collision, and as the severity is higher the probability is reduced to compensate.

Having said that, more recent tram-train designs do include extra crashworthiness so are intermediate between trams and trains. But that could possibly be argued out in a safety case, based on alternative provisions being made instead.

My assumption was that the standard they need to meet wasn't necessarily fully commensurate with those required for actual trains, but higher than the standard for trams: as you say, an intermediate level. I probably didn't express that as clearly as I should, as I was tired!
My point was that simply being high-floor and running (in part) on former rail alignments does not make the M5000s tram-trains, or particularly close.