The announcement comes just over a year after the government last August announced cheaper tolls on motorways in specific areas.
Despite an increase in the number of vehicles using the motorways, revenue generate from tolls has dropped by an overall €13 million.
However, the government said that the 15 percent “discount” in toll fees has saved motorists on these motorways a total of 24 million euros.
Transport and Infrastructure Minister Pedro Marques explained that the cost reduction has allowed for greater mobility in the region, with an increased use of motorway.
The news comes as it was revealed this week that tolls would be raised by an average of 1.42 percent at the beginning of 2018 in accordance with the projected inflation rate.
The toll reduction last summer, despite the savings motorists are said to have made, was challenged at the time for being too little.
Expectations had been that discounts could be around 50 percent, with associations set up to promote the interests of motorists, arguing it would make little difference to reducing traffic on congested secondary routes and that it was more a token gesture than one of any particular value.
During the announcement, Pedro Marques said the reduction could imply losses in revenue for the state in the region of 13.6 million euros, which is not far off the figure revealed this week.
However, a study commissioned in 2015 by the government suggested that reducing tolls would actually generate revenue, with estimates pointing to a figure of 22 million euros.
The Socialist government had at the time explained that this study formed an integral part of their decision to lower tolls this summer.
One of the biggest potential earners for the state in reducing tolls would be the Algarve’s A22 motorway, researchers revealed.
Researchers said that if reductions were to go up to 35 percent, the state would still collect more money from tolls than if it were to keep prices unchanged.
The Socialist government had previously said it was against the total abolition of the tolls because “it is absolutely imperative and necessary to make sure the budget remains balanced”.
A month before being elected Prime Minister, António Costa referred to the EN125 as “a massacre” and a “cemetery”, due to an increase in traffic on this road and a drop on the A22. António Costa further said that one of his party’s priorities, if they were elected to govern, would be to go one step further and “eliminate” tolls and “create better access routes” in the Algarve and in the countryside.