The two tribes planning to build a casino in East Windsor are to set aside some gaming revenue to help six municipalities that will bear costs of increased traffic in the region.

One town, however, was left out of the law, and the mayor there was miffed.

The bill signed into law by Gov. Dannel P. Malloy on Tuesday instructs the Mashantucket Pequot and Mohegan tribes to deposit $4.5 million into a special fund annually. Six shares of $750,000 each will go to Hartford, East Hartford, Enfield, South Windsor, Windsor Locks and Ellington.

The money is intended to help pay for the expected increase in regional traffic and associated issues, such as road maintenance and law enforcement. Windsor, however, was not included in the grant program.

Enfield, Ellington and South Windsor border East Windsor, and Windsor Locks is directly across the Connecticut River, connected by I-91. Hartford and East Hartford were included because they are nearby "distressed communities."

Like Windsor Locks, Windsor is a cross-river neighbor of East Windsor, although not connected by a highway. Windsor Mayor Donald Trinks said Tuesday that the town will nevertheless bear extra costs associated with the casino and should have been included in the grant program.

"I can't understand why some towns were included and some weren't," Trinks said. "Without question we'll see some of the negative spillover."

Several towns near Foxwoods Resort Casino and Mohegan Sun receive aid that the tribes deposit in a state fund, Sen. Tim Larson, D-East Hartford, said. But Larson could not say exactly why Windsor was not among the towns receiving funds.

State Rep. David Baram, a Democrat whose district includes Bloomfield and part of Windsor, said Wednesday that he asked legislative leaders about Windsor's exclusion.

"I was told it was primarily for towns directly abutting East Windsor that would be negatively affected by increased traffic and public safety resources," Baram said.

Rep. Brandon McGee, a Democrat who represents Windsor and Hartford, said Tuesday that despite Malloy signing the bill, he expects to find a way to direct additional funding to Windsor.

Those set to receive the grants said the aid will help. South Windsor Mayor Carolyn Mirek said Route 5, which runs through the western side of town, may become a main route to the casino.

"They are going to be right next door to us," Mirek said. "We will be impacted by this in terms of traffic and we will need to make sure our public safety services are not impacted. So if we need to allocate money for road and infrastructure improvements or add more kind of services to deal with the impact of the casino, the funding is a good thing."

East Hartford Mayor Marcia Leclerc said her town's inclusion was a bright spot amid more bad news on state aid.

"We are always grateful to hear of new sources of revenue coming to our community," Leclerc said, "especially given the announcement yesterday that East Hartford would be negatively impacted over $8 million with the newest budget release."

Courant staff writer Peter Marteka contributed to this story.