SMRT has been fined $1,700 for bus service lapses between June and November last year.

While it is the transport operator's biggest fine to date, the amount would have been $34,000 under a new penalty framework. The new rules will kick in for the next assessment period of December last year to next month.

When announcing the revised framework last month, the Public Transport Council said the heavier fines were to show how seriously it takes lapses in bus service.

SMRT's buses were overloaded on two instances between June and November, while they failed to meet the scheduled intervals on 15 occasions.

SMRT Buses vice-president Tan Kian Heong told Chinese daily Lianhe Zaobao that the latter was caused by a shortage of bus drivers during a two-day illegal strike last November.

He also said severe traffic congestion along Woodlands Road in September had led to overcrowding on service 178, while an accident along the Bukit Timah Expressway in October had the same effect on service 966.

Mr Tan added that these two instances of overloading were beyond SMRT's control. That is why he wants the authorities to take into account the impact of external factors when assessing service standards.

The other public transport operator, SBS Transit, had a spotless record during the same review period. Its highest fine was $9,300, for the period between December 2007 and May 2008.

This is the last six-month service review under the previous penalty framework, which slaps a fine of $100 for each bus service that fails to meet a daily standard. Last month, the Public Transport Council raised this to $2,000.

For monthly standards - such as keeping the breakdown rate on all services lower than 1.5 per cent - the fine has been raised from $10,000 to $100,000 for every failure.