The 2015 toll rate adjustment is not solely based on profits, but also to provide services and safe and comfortable journey to highway users.

The Association of Highway Concessionaires Malaysia (PSKLM) said the adjustment was also important to ensure continued investor confidence.

It said on average, 50 per cent of the revenue collected by the concessionaires was to repay loans, operations and maintenance (20 per cent), upgrading and repairing (15-20 per cent), and returns to shareholders and others (10 per cent).

"It is incorrect to claim that the adjustment of toll rates is solely for the purpose of reaping huge profits," the association said in a statement, Tuesday.

PSKLM said a call for the toll rate adjustment or compensation payment to be frozen was not realistic as it would affect the ability of PSKLM members to effectively manage the highways.

INFOGRAPHICS: Toll hike on 18 highways effective October 15

It said that according to the Toll Highway Privatisation Policy in the early 80s, the concessionaires would bear all the expenses incurred in building highways and authorised to collect tolls for a specified period.

Under this policy, one of the key elements featured in the agreement is future toll rate revision, taking into account various reasons such as traffic projections, financing costs, inflation, and maintenance and operation costs, it added.

PSKLM said the agreement with the concessionaires should be respected in order to maintain the credibility of all parties involved, especially in terms of future investor confidence.

"For highway users, every agreement has ensured that the rate adjustment is made in gradually and not a sudden increase to avoid burdening them.

"Previously, compensations had been paid by the government when toll rates were not adjusted," it said, adding that during the 2008-2013 period, the government paid over RM1 billion in compensation in the interest of the people.

Several main highway concessionaires in the Klang Valley had announced hikes in toll rates of between 10 sen and RM6 effective Thursday.