EVERY time someone strays onto the MRT tracks, thousands of other commuters are likely to face delays of up to an hour - more, if the perpetrator is hit by a train. So far this year, 21 people have fallen or found their way onto the tracks. Last year, 31 people did so, and 30 the year before, an SMRT spokesman said.

More than 70 per cent of the cases were intentional, that is, the perpetrators were drunk, high on drugs or trying to commit suicide.The others had unintentionally slipped onto the tracks when they felt faint, lost their balance or were careless.

All the cases took place on the above-ground portions of lines operated by SMRT. As a safety measure, the Land Transport Authority (LTA) said it would complete installing half-height platform screen doors at three above-ground MRT stations - Pasir Ris, Jurong East and Yishun - by the end of next year.

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