The earthy, pungent and oddly beguiling bouquet of hot, fresh-poured asphalt wafted into the night air on southbound Interstate 95 between Baltimore and Washington.
It's an aroma Mike Strong loves. "When I smell that, I know springtime's here," said Strong, a project engineer for the State Highway Administration.
While Strong savors the fragrance of asphalt, nighttime motorists on I-95 have been breathing the exhaust fumes of traffic jams as four lanes of traffic in each direction are reduced to two lanes five nights a week on the busy interstate.
The resulting backups on a roughly 5 1/2 -mile stretch of I-95 in Howard County are the burden drivers must endure to enjoy the benefits of the $15 million resurfacing project the highway agency launched this spring.
With the arrival of summer, Strong will be enjoying the smell of asphalt even more as the state's highway contractor lays 3,000 to 4,000 tons a night Sunday through Thursday as part of Maryland's never-ending effort to keep the highway surface smooth despite the constant pounding of some of the nation's heaviest traffic.
By the time the project is done, about 130,000 tons of hot mix asphalt - heated to 325 degrees - will be poured.
For daytime drivers in the Baltimore-Washington corridor, the roadwork has had a negligible traffic impact except for the feel of a roughly ground-down surface in some places and a smooth new surface in others.
But for nighttime drivers, the lane closings have brought delays of as long as 40 minutes on some nights - a headache, but hardly comparable to a bad day on the Bay Bridge. State highway officials say that on most weeknights, motorists can get through the I-95 construction zone in about 15 minutes compared with the usual five.
Strong said that if Maryland tried to get the I-95 project done during daylight hours - as he said many other states do - the traffic problems would be overwhelming.
"You would probably see it backed up to Baltimore," he said.
State highway officials say they regret the inconvenience to motorists, but the closings are the price that must be paid for a smooth ride. They say they need to give contractors adequate time to work at night so they can finish the project while the weather is still warm enough to pour asphalt, which won't set properly unless the temperature is 55 degrees and rising, according to SHA spokesman Dave Buck.
Ragina Averella, Maryland spokeswoman for AAA Mid-Atlantic, said she has heard no complaints from members about the project. "It's a necessary inconvenience," she said.
Before the work began in early April, the condition of the roadway in the construction zone - running from just north of Route 100 to a little south of Route 32 - was "terrible," Strong said. The last time the section had received a full resurfacing was in the early 1990s.
Strong, who at 45 has been a project inspector for 25 years, said Maryland highway officials make every effort to carry out road work on busy interstate highways at night, when traffic volumes are lower than during the day.
But slowdowns are unavoidable when highway workers begin the process of taking away half of the interstate's capacity at 8 p.m., while traffic volumes are still relatively high. Not until after 11 p.m. do volumes - and the resulting congestion - drop off considerably.
Closing down two lanes of a four-lane road is no simple matter. It's a highly choreographed undertaking - supervised by a certified "movement of traffic" expert - involving significant risk to the workers who carry out the gradual seizure of motorists' territory so that the paving crews can do their job.
The first step is to put up signs warning motorists of the lane closings ahead. The hope is that they will begin to move over well in advance of the zone, but many resist the message until they come right up to the work zone, Strong said. He believes these last-minute lane-changers are the main cause of backups.
The critical tool for establishing control of the zone is what highway workers know as a "barrel taper." It consists of a row of orange-and-white barrels, strategically deployed to force motorists into the lanes that will remain open.
On a warm, clear night last week, workers for Baltimore contractor P. Flanigan and Sons Inc. could be seen moving the barrels into place under the protection of a truck bearing an electronic sign with a flashing arrow directing traffic into the left lanes.
As they move up the road, the workers gradually station each barrel a few inches farther into the roadway until the entire lane has been claimed for the contractor. "What you're looking for is a nice, smooth transition," Strong said.
Once the taper is established, workers use cones to block off the lane. Then the process is repeated to claim a second lane.
Buck said it takes about an hour to an hour and 15 minutes to shut down two lanes of I-95 in each direction. Only then can the paving crews get about their business.
In the morning, the paving will stop sometime around 4 a.m., and workers begin the process of removing the cones and barrels in time for the start of the morning rush hour. The contractor is required to reopen the road by 5 a.m. and faces a fine if the deadline is missed, Strong said. That leaves the workers about seven hours to put down asphalt.
Strong, who lives in Sharpsburg, estimates that 95 percent of the traveling public understands the necessity of the project and appreciates the road crews' work.
Then there's the other 5 percent.
"They try to swerve at you and cuss at you, and you hear it," he said. "Luckily, nobody's been throwing anything at us yet."
While the current project hasn't seen any serious injuries, Strong said, workers can never let their guard down. He once had to jump on the hood of a police car to get out of the way of a driver who would have hit him, he said. On one project in Montgomery County, Strong said, a worker was hit by a vehicle, bounced off the side of a tractor-trailer and landed in hot asphalt. The man survived, but with severe burns and other injuries.
As if to underscore Strong's point, one motorist near the work site a reporter was visiting abruptly veered between cones into a lane where a paving crew had just laid hot asphalt. Closing quickly on a steamroller, the driver just as quickly darted back into the open lane - narrowly avoiding a collision with a tractor-trailer.
Mike Klohr, Flanigan's project manager, said he sees such a stunt about once a month.
For now, the contractor is working on putting down a base coat of asphalt - poured at 2 1/2 inches deep and compressed with steamrollers to 2 inches. Early next month, Klohr said, workers will begin pouring the surface coat.
State highway officials said they expect that phase of the project - and the double-lane closures - to be finished about mid-September. But Klohr said single-lane closings will continue through mid-November as the contractor performs such tasks as replacing topsoil at the road's edge.
Strong said that with an improved asphalt formulation, his guess is that this new surface will give motorists a smooth roadway for 15 to 20 years.
"We hope that when we're done, we have something here they can be proud to ride on," he said.