As the 2025 NASCAR Cup Series playoff’s second round heads to New Hampshire Motor Speedway this weekend, fans can expect plenty of thrilling racing action on the track and heavy traffic on the roads in Loudon, New Hampshire. The high-profile playoff race is scheduled for Sunday, September 21, at New Hampshire’s 1.058-mile flat oval track, with the event set to begin at 2 pm ET.According to NBC Boston, the New Hampshire Department of Transportation confirmed that over 42,000 spectators and 15,000 vehicles are likely to come to watch Sunday’s Mobil 1 301 at “The Magic Mile.” The NASCAR Cup Series Nashville weekend is set to kick off on Saturday with additional races like practice and qualifying. The traffic is likely to occur in the afternoon, but the biggest congestion will be immediately after the race ends.State transportation officials have announced major traffic control plans to accommodate the thousands of fans heading to Loudon for the NASCAR Round of 12 playoff opener.The key traffic control measures will be in place around New Hampshire, affecting I-93, I-393, and NH Route 106. From about 3:15 to 9:00 p.m., several I-93 ramps, including exits 14, 15E, and 15W, will be closed with detours set via Stickney Avenue, Exit 15W, and Exit 16.On NH Route 106, morning traffic will be reconfigured to prioritize northbound lanes toward the speedway, with left turns restricted at multiple intersections. In the afternoon and evening (3:00–8:30 p.m.), northbound traffic will be detoured onto NH Routes 129, 107, and 140, while southbound traffic will expand to four lanes near the speedway before gradually merging back to two lanes near Concord.Access from side roads will be limited to right turns only, and Clough Hill Road will be closed to non-local traffic. Uniformed officers will direct traffic at key intersections and exits.Who is the favorite to win the NASCAR Round of 12 opener at New Hampshire?Christopher Bell, the driver of the #20 Joe Gibbs Racing Toyota, is the favorite to win at New Hampshire Motor Speedway. Bell is coming off a win at Bristol Motor Speedway and has a history of success at “The Magic Mile.” He is the defending winner of the event and has won here twice.According to BetOnline Sportsbook, the #20 JGR driver has the highest odds at +325. His teammate Denny Hamlin sits second at +450, followed by Kyle Larson at +650, Ryan Blaney at +700, and Chase Briscoe at +750.Watch the 2025 NASCAR Mobil 1 301 at New Hampshire on NBC Sports and USA Network.