SBS Transit, which runs the majority of bus services here, said it detects about 10,000 cases of cheating every month - which works out to more than 330 cases a day.

'Fare evasion is a serious problem for us,' said its spokesman Tammy Tan.

Meanwhile, SMRT said it had about 1,470 cases every month last year - almost 50 cases a day.

According to statistics in 2005, cheats cost the bus companies $9 million in fares each year.

To help stem the losses, the Public Transport Council (PTC) announced that from July 1, commuters caught not paying or under-paying their bus and train fares will have to pay a $20 penalty.

Currently, the penalty for cheating on trains is $50, but from July, the same penalties will be imposed for both modes of public transport to remove the disparity.

Those who use a concession card they are not eligible for will have to pay $50.

Among those caught cheating by SBS Transit, half paid less than what they should by tapping their ez-link cards at the exit way before they were due to alight.

One in three caught was misusing concession cards, while one in four did not pay fares at all, said SBS.

In one case of fare cheating two years ago, a woman was caught using a primary school pupil's concession card while boarding an SBS bus.

But even though bus drivers and ticket inspectors weed out hundreds of fare cheats every day, many more get away.

In the latest available statistics from 2005, TransitLink estimated there are about 42,000 cases of fare evasion on buses every day.

It derived this number by multiplying the total number of trunk service trips by the average number of cases of fare evasion on each trip.

The average fare lost is 60 cents.

Before the penalties kick in, bus operators will issue advisories to fare cheats and put up posters at interchanges and MRT stations to inform commuters of the tougher action.

From July 1, those who are caught cheating on their bus and train fares can either pay up on the spot or at TransitLink's ticket offices and Add Value Machines within 14 days.

Those who do not do so by then can be fined up to $1,000. Subsequent offenders can be fined up to $2,000 and/or be jailed up to six months.

While cheating on buses is rampant, it is less common on trains.

SMRT said it sees about 105 cases of train fare evasion a month, while SBS, which runs the North-East Line, gets about three cases every month.

Those caught usually follow closely behind paying passengers to get through fare gantries.

Others do not pay for children travelling with them.

ghimlay@sph.com.sg