Many experts consider the now-voluntary dynamometer test more accurate, but many motorists believe it's more of a hassle. A major complaint is that the test is intrusive because testing center attendants - not vehicle owners - drive the car on the treadmill.
"I've been hearing things about the other test," said one motorist who opted for the tailpipe test on Tuesday. "He says it's easier to pass, but I've been hearing other things. I think I'll just take my chances with this test.
"I didn't want someone else being in here behind the wheel."
Testing officials - who insist the test is just as safe and more accurate - said they have heard rumors that the dynamometer test can damage the car. They emphatically denied that was the case.
Still, some drivers just don't trust it.
"I have a constituent who swears his car ran fine until he did the dynamometer, and now his back end rattles," said Del. Robert A. McKee, R-Washington.
Public outcry across the state has led to several delays in the expanded program, which originally was to begin two years ago. Legislation has been submitted during the current General Assembly session to delay or abolish the testing.
But Glendening warned that failing to participate in the expanded emissions program could lead to intervention by the federal Environmental Protection Agency. That could mean stricter environmental standards placed on industries and hurt economic growth, he said.
"The short and long of it is, what does this mean to business?" said Del. J. Anita Stup, R-Frederick/Washington, a member of the House Environmental Matters Committee. "I don't know, but it is kind of spooky."
The issue has been particularly sensitive in Washington County, where many residents have asked why the county has to be subjected to the same pollution restrictions as the more-polluted metropolitan areas.
"If Garrett and Allegany counties aren't in the program, I don't think we should be," said Del. John P. Donoghue, D-Washington.
Several motorists waiting for the test at the Hagerstown Vehicle Emissions Inspection Program station at 12100 Insurance Way on Tuesday questioned why large tractor-trailers are exempt.
Fairplay resident Ed Lewis, whose father-in-law was having his car tested, said it did not think the test was necessary.
"The vehicle runs fine - you don't see black smoke coming out of there," said Lewis.
The chief pollutants in the county come not from cars, but from large diesel vehicles that converge on the county from other areas.
State officials concede the point, but emphasize that is why the test is needed. Smog can build in the county, in part due to pollution that drifts into the region from areas with smokestack industries, said Susan Woods, a spokeswoman with the state Department of the Environment.
Also, the county is included in emissions testing because it exceeds statistical limits on population and commerce, said Caryn Coyle, a special assistant for air and radiation for the agency.
"There's enough activity there that causes pollution," Coyle said.
Despite lingering resentment toward the testing requirements, concern over the dynamometer test appears to be waning, officials said.
Coyle said 58 percent of those having their vehicles tested in Washington County are opting to take the dynamometer in exchange for a $2 coupon, which reduces the cost of the test to $10. That's the best participation in the state, where on average, 40 percent of motorists are opting for the dynamometer test.
"That's great," Coyle said.
Mike Sims, state representative at the Hagerstown station, said education efforts have convinced people that the dynamometer test is superior.
"A lot of it's word of mouth," he said. "A lot of mechanics realize it's the better test and are recommending it. A lot would take it even if were the same price, I believe."
Chris Davies, manager at the testing station, said the dynamometer test is better because it more accurately simulates highway driving.
"The catalytic converter will actually get cherry-red hot," he said. "It's a better burn. It's a cleaner burn."
Some drivers said they prefer the idle test but would not have a serious objection to switching to the other.
"Someone told me it was faster," said Cearfoss Pike resident Floyd Kline. "I was in a hurry to get through."
Others are confused. John Mosley, who is originally from Missouri, said he is not used to the test.
"It's all a bunch of Greek to me," he said.
Staff Writer Brendan Kirby contributed to this story.