Operators governed by different rules on raising tolls
The Western Harbour Tunnel Company is allowed to automatically increase tolls each year - but only if government audits find revenue for the year is lower than the amount contractually allowed.
This contrasts with the Eastern Harbour Tunnel, for which a more complicated application procedure to increase tolls is required, involving approval from the Transport Advisory Committee and the Executive Council.
Over the past few years, the Executive Council has rejected repeated applications by the eastern tunnel operator to increase the toll, on the grounds that an increase was not justified because of the company's strong financial position.
The maximum toll for the western tunnel is $50 a car, but under the current concessionary tolls, users are charged only $40. The next projected maximum toll is $60. The eastern tunnel charges $15 per car.
The operator of the western tunnel has long argued for its maximum allowable tolls to be even more easily adjusted.