It is a slow and icy ride to work for commuters on Tuesday morning.

A jackknifed tractor trailer on the New Jersey Turnpike between #6 (PA Turnpike) and #5 (Mt. Holly) (Via Waze, BanderAbuatt)

Early morning drivers have been encountering snow covered roads with reduced speeds. Sections of the New Jersey Turnpike, Garden State Parkway and Atlantic City Expressway are all reduced to 35 MPH in South and Central Jersey, where snow is falling the hardest.

"Slow and steady wins the race" says New Jersey Fast Traffic's Bob Williams. He also advises drivers to leave extra distance between vehicles. "And remember, its the law in New Jersey to clear all the snow off your car," Williams adds.

New Jersey State Police tweeted that they received calls for 120 crashes and 325 motorist calls on Tuesday.

NJ Department of Transportation spokesman Stephen Shapiro says more than 2,500 plows and salt spreaders worked overnight to clear road surfaces. "State highways are passable with the best conditions in North Jersey," he said. "There is heavier snowfall in Central and South Jersey so roads may have snow on them as crews continue to work to clear highways."

The brine put out by many municipal road departments on road surfaces doesn't work as well when temperatures drop into the teens and single numbers.

An NJ DOT plow truck on Route 31 in Ewing (Dan Alexander, Townsquare Media NJ)

"Because it's so cold, with temperatures in the teens, salt and brine are mostly ineffective," says Townsquare meteorologist Dan Zarrow. "Salt works by lowering the freeze/melt point of water/ice. It's much easier to clear roadways with ice that melts at 26 or 27 degrees, compared to the usual freezing mark of 32 degrees." The only way the snow and ice will melt today will be if temperatures rise a bit, and/or we get some direct sunshine. Both should happen by this afternoon."

Shapiro said NJDOT treats its salt with liquid calcium, which allows it to be more effective in extreme cold.

A number of schools that initially reported delayed openings have now announced they are closed for the day.

NJ Transit is cross-honoring tickets across its entire system on trains, light rail and buses.Amtrak's Northeast Corridor is operating on a modified schedule between Washington D.C. and Boston.