MIAMI -

South Florida drivers could soon be forced to shell out more cash for tolls on several expressways.

MDX, the Miami-Dade Expressway Authority, is proposing a toll hike for SR 836, the Dolphin Expressway. A similar rate hike is being proposed for SR 112, the Airport Expressway.

"To me it is a tax, an unnecessary tax," a woman named Margaret told Local 10's Terrell Forney. She declined to give her last name as she protested with 40 other people about the proposed toll hike, which could raise rates by as much as 50 percent.

A grassroots group called 'RollBackTolls.com" is mounting a movement to spread the word about the proposed idea of higher tolls.

Last year, MDX collected more than $122 million dollars in tolls on just five of Miami-Dade County's expressways.

In addition to raising the tools on the 836 and 112, the agency is also looking to add a higher surcharge for non-Sunpass users who are billed by license plate. The move could double the posted toll amount.

The agency would also implement automatic toll rate increases that would start in 2015. They would ensure regular toll hikes down the road would match inflation.

Miami-Dade Commissioner Xavier Suarez is joining the fight against any proposed toll hikes. He sent a two page letter to MDX on Monday, protesting the cuts. In it, he called the increase a "cruel and unusual punishment for urban dwellers, who have very little alternative."

The commissioner's letter also mentioned MDX's growing debt. When the agency was formed 16 years ago, it assumed a debt of $60 million. Today, it owes over $1.2 billion. Tolls are normally used to pay down those debts.

Drivers will have a chance to sound off on the proposed toll hikes in a meeting at the MDX offices on March 19th.

Margaret and the other protesters at Monday's meeting plan to fight any proposed increases.