50 will be supplied by Alexander Dennis (Singapore) for a contract sum of about $34 million, and 50 will be supplied by ST Engineering Land Systems for around $30 million. This is the first major order of its kind, after the LTA carried out a trial of three-door buses earlier.

Tower Transit operated a three-door, double-deck bus on Service 143 from March to September 2017, and SMRT Buses operated a three-door, single-deck bus on Services 190 and 901 from June 2017 to January 2018. The authority said commuters "generally welcomed the additional door on these buses, as it made boarding and alighting smoother and quicker".

Because of the encouraging results of the trial, it called a tender to buy 100 such buses last May. The regulator and fleet owner said on Thursday (April 25) that it awarded the contracts to the two companies after evaluating all bids based on criteria including price, tenderers' experience, track record, technical capabilities and compliance with local regulations.

Both the companies are the LTA's existing bus suppliers, with Alexander Dennis (Singapore) accounting for about 4% of its public bus fleet and ST Engineering Land Systems, 23%. The new buses will arrive in Singapore in batches and be deployed on the road from next year.