K BARNES' letter about the Great Heck train crash is too sweeping in its assumption that he is an expert on sleep deprivation (October 29).

Granted there is a time around late afternoon when people in normal routines become tired. This is often caused by the lack of a substantial breakfast and lunch rather than sleep (blood sugar level deprivation).

As a livestock farmer for 50 years I can assess the affects of sleep deprivation having had countless nights up awaiting the arrival of calves and having to carry out the succeeding day's work schedule as normal.

Each individual will respond differently to going without sleep. I can also say that having done a full physical day's work starting at 6am prior to a night without sleep causes a crisis point somewhere between 2am and 6am.

K Barnes' analogy of "colleagues going on the golf course" after a night time callout is far from the same as sitting in an enclosed heated vehicle driving along a monotonous motorway.

I once had three nights up out of six. On the Wednesday after being up all night I was asked by a neighbour to drive her to Leeds to be with her dying mother. I agreed on condition that the car windows would be kept open and the fan ventilation set cold air only.

Gary Hart may well have felt "all right" when he set off from home, but 20 miles on along the monotonous roads he has been too stupid to realise he was incapable of continuing his journey.

From a photograph of the road (above) where he veered off, it was obvious that he was not controlling his vehicle. If he had been positively conscious he would have braked long before going over the edge or turned to avoid the track.

E L Thompson,

Pond Farm,

Crambe, York.

Updated: 11:22 Thursday, November 04, 2004