CONCORD, N.H. — The New Hampshire Liquor Commission is ramping up efforts to prevent drunken driving during the holiday season by increasing undercover monitoring of establishments serving alcohol and partnering with the state police to increase patrols.

A $25,000 grant from the National Liquor Law Enforcement Association will help pay for the effort through Jan. 1. The money will help improve the state’s ability to target bars and restaurants that serve already impaired patrons. Enforcement officers plan to visit bars and restaurants to speak with owners, employees and patrons about the dangers of drunken driving.

About 50 percent of impaired drivers have recently left a bar or restaurant, said James Wilson, director of the liquor commission’s enforcement division.

Establishments and their employees who overserve customers are subject to fines or other penalties including criminal or civil prosecution and liquor license revocation. The state’s been collecting “point of last drink” data since 2008, but hopes to make the system more robust by improving the ability to share data and map geographic trends.

“This data sharing is a crucial investigation tool,” Wilson said.

For the undercover operations, the commission will send officers in plain clothes into bars and restaurants to observe serving practices. If enforcement is necessary, a uniformed officer will be called in.