Last month, for the second time in 18 months, former Eagles quarterback Donovan McNabb was arrested in Arizona for driving under the influence. According to police investigators, McNabb was caught driving with a blood-alcohol concentration of 0.171 percent, twice the legal limit. In a video of his arrest, McNabb contends he was on cold medication.

McNabb's arrest shines a spotlight on the issue of repeat DUIs.

"Anyone can have one DUI," said Helen Weigand, director of DUI services at Livengrin Foundation, a nonprofit addiction-recovery center based in Bensalem, who lost her 22-year-old daughter 20 years ago to a crash involving a drunken driver. "You don't have to be an alcoholic or have a drinking problem. You just have to make a bad choice.

"But more than one DUI, along with other behavioral problems - that's when you need to seriously look at things."

Experts say most people who drink and drive do so many times before they are caught.

"The problem with alcohol, you can drive 35, 50, 100 times and don't get caught, and then you get caught," said DUI lawyer Joe Kelly of Port Richmond, who has defended about 15,000 DUI cases. "You think you're invincible, but you eventually have to pay the price."

"More often than not, a repeated DUI is a sign that there are more significant problems," said William Lorman, vice president and chief clinical officer at Livengrin. "Although every case is individual, statistically, two or more DUIs increase the risk of alcohol-use disorder. By the second DUI, and certainly third or fourth, things can be out of hand."

The number of alcohol-related crashes in Pennsylvania dropped to 10,550 in 2014 from 11,041 in 2013. Still, there were 333 alcohol-related deaths in 2014. On average each day, 29 alcohol-related traffic crashes occurred, and 20 people were injured, according to the Pennsylvania Department of Transportation.

In meting out punishment for DUI, Pennsylvania considers the number of violations a person has had over the last 10 years, as well as blood-alcohol concentrations.

"The real issue is how much does a person usually drink, and how much have they built up their tolerance to alcohol," said Lorman. "People who have a [blood-alcohol content] of 0.27 [percent] can still be functional because they've built up a high tolerance."

A person who has a high tolerance "can drink a lot more than someone who is alcohol naïve," he said.

"It's this tolerance that makes a person think he could go out and drive," he said. "But while you may believe you're thinking and acting straight, you can't react as fast with alcohol in your system."

And you may be impaired even before hitting the legal limit - now 0.08 percent in all states.

"We know that even a small amount of alcohol affects the ability to perform complex behaviors like driving," said Charles O'Brien, director of the Center for Studies in Addiction at the University of Pennsylvania.

Evidence of impairment can include the decision to drive in the first place, vision and hearing difficulties, problems with reaction times, and drowsiness behind the wheel.

O'Brien notes that in Europe, many countries have zero tolerance for drinking while driving - which means any amount of alcohol in the blood counts as DUI.

"People have to realize how dangerous it is," said O'Brien.

"One drink can lead to another, and they can make very bad judgments. They might not be alcoholics, but frequent DUIs are a very bad sign of high-risk behavior."

Judges can order ignition interlock devices to be installed in cars, which require drivers to breathe into the apparatus before the car will start. O'Brien also recommends a device that tests alertness. Electronic skin devices that sound an alarm can also prevent people from drinking alcohol.

In addition, there are new drugs, including Vivitrol (naltrexone), a monthly injection that reduces cravings for alcohol, when an alcohol disorder has been diagnosed.

"We try to explain to clients that a DUI impacts every area of your life," said Weigand. "It impacts your license, your freedom, and it's costly. It can take them away from their families. If you're able to see all of this, you won't make that choice again. Alcohol isn't that important to you.

"Someone who doesn't see that? Well, they have a problem."