Johnson and six passengers were taken to Washington County Hospital for treatment.
Passengers Wynette McDonald, 27, of Fort Washington, Md., and Marilyn Mease, 38, of Riverdale, Md., were admitted to the hospital, according to a hospital information clerk. Both were in fair condition Sunday night.
Johnson and passengers Diane Wingate, 20, of Hyattsville, Md.; Steven Davis, 19, of Riverdale, Md.; Leandre McCoy, 15, of Temple Hills, Md.; and McKinley Allen, 19, of Capital Heights, Md.; were treated and released, according to the hospital.
Group members told police they were employees of Inventory Auditors Inc., in Fredericksburg, Va., on their way to Martinsburg, W.Va., to conduct an inventory.
Accidents caused by the rainy weather kept police busy over the weekend, but most of the accidents weren't bad enough to require a report, authorities said.
A Hagerstown woman went to the hospital Sunday afternoon after her car slid off Mount Aetna Road and struck a guard rail, according to the Washington County Sheriff's Department.
The accident happened around 12:30 p.m. near Mapleville Road, troopers said.
Ruth Ann Robinson, 52, was treated at Washington County Hospital and released, according to a hospital information clerk.
The guard rail was pushed into a telephone cable box, temporarily cutting off phone service in the area, deputies said.
Three teenage girls were taken to the hospital late Saturday when their car was rear-ended by a Mercersburg, Pa., teen at the intersection of Md. 60 and 62, according to the sheriff's department.
Jon Molchan, 19, of 14340 Dutchtown Road, was charged with failure to control speed to avoid a collision and negligent driving, deputies said.
Two 15-year-old girls and a 16-year-old girl riding in the struck car were taken to Washington County Hospital, deputies said.
Police hadn't released the girls' names on Sunday. No reports on their conditions were available from the hospital.
Driving too fast on slick roads caused most of the more than 15 accidents Maryland State Police handled over the weekend, said Trooper 1st Class R.A. Plante.
Drivers should make allowances for the slickness by driving a little slower than normal and giving more room between them and the car in front of them, Trooper Rick Stotelmyer advised.