WASHINGTON — Bank customers who overdraw their checking accounts would get new protections from excessive penalties under legislation proposed today by the Senate banking committee chairman.

The measure unveiled by Sen. Christopher Dodd, D-Conn., would give people a choice in whether they want to participate in overdraft programs that charge fees for covering ATM withdrawals and debit card transactions.

Most banks now automatically enroll customers in overdraft programs. That means a sale will go through if a person spends more than is in his or her account, but the customer will be hit with a fee, usually in the $25 to $35 range even if the overdraft is just a few dollars.

The unwary customer who makes several overdrawn purchases in a day could be charged a $35 penalty for each purchase.

Several major banks, in anticipation of congressional action, have already said they will start letting people opt out of overdraft programs. Some have also said they will lower their fees.

Dodd cited estimates that banks stand to collect a record $38.5 billion in fees for customer overdrafts this year.