The person spoke to The Associated Press on the condition of anonymity because they could not discuss the case publicly.
TMZ first reported the details regarding the vehicle.
Stevens, a former tight end for the Seattle Seahawks, was pulled over in Manhattan Beach, California, about 1:30 a.m. Monday for driving without headlights. Solo was the only passenger in the car but she was not arrested or detained.
U.S. Soccer on Wednesday suspended Solo from the national team for 30 days. She will not travel to a pair of exhibition matches next month in Europe.
Solo was in Southern California for training camp with the team, which is preparing to play in the World Cup starting in June.
"I think it's best for me to take a break, decompress from the stress of the last several months, and come back mentally and physically ready to positively contribute to the team," Solo said in a statement following her suspension.
It was the latest off-field trouble for the 33-year-old Olympian. Earlier this month, a judge dismissed two misdemeanour counts of domestic violence against her. The charges stemmed from an altercation with her half-sister and 17-year-old nephew at a party in Washington state last June.
Solo had pleaded not guilty in that case, and she continued to play for the U.S. team and with her National Women's Soccer League team, the Seattle Reign, while awaiting trial.
Her last appearance in a match with the national team was in December, when she started in a scoreless draw against Brazil in the championship game of the 2014 International Tournament of Brasilia.
"During our current national team camp, Hope made a poor decision that has resulted in a negative impact on U.S. Soccer and her teammates," coach Jill Ellis said in a statement Wednesday. "We feel at this time it is best for her to step away from the team."
Solo will be eligible for reinstatement after the suspension, pending review and approval by U.S. Soccer and Ellis.
U.S. Soccer did not comment further on the matter.
The suspension comes at a critical time for the U.S. team. Following the exhibition matches in February, the U.S. team will play in the Algarve Cup in March before opening World Cup play on June 8 against Australia in Winnipeg, Manitoba.
Stevens was released with a citation to appear in Los Angeles Superior Court on March 19. The couple lives in Kirkland, Washington.