Drinkers, beware. Even if you drink regularly, you are unlikely to be able to tell if you are intoxicated.
This is because there are various factors which affect how much a person can drink and how quickly a person becomes drunk, experts told The Straits Times.
Last month, former minister of state Chan Soo Sen, 56, failed a breathalyser test while driving home from a charity function where he drunk red wine.
Chan was tested with 50 micrograms of alcohol per 100ml of breath, in excess of the legal limit of 35 micrograms. He was fined $2,000 and given a one-year driving ban last Thursday.
Typically, a glass of wine or champagne at dinner will not cause a driver to exceed the legal limit - unless he downs it in a gulp, said Dr Tan Chi Chiu, consultant gastroenterologist with Gastroenterology and Medicine International.
But different people react to alcohol differently, depending on factors such as the rate of consumption, degree of hydration and how fast their bodies break down alcohol, said family physician David Fong.
For example, women are smaller and have a lower percentage of body water than men, so they tend to be more sensitive to alcohol, he noted.
Moreover, different types of alcoholic beverages have varying levels of concentration, so people who appear to drink little could still be absorbing a lot of alcohol, said Dr Tan.
"Assuming that two people drink exactly the same volume, one of spirits and the other of beer, the one drinking spirits will have taken much more alcohol into his or her system than the one drinking beer."
Even frequent drinkers might not be aware of such factors. Out of 10 regular drinkers that The Straits Times spoke to, only two were aware that age also affects how the body processes alcohol.
Motorists can be charged with drink driving even if they are under the legal limit, as long as they do not have proper control of the vehicle. Last year, 2,917 people were arrested for drink driving.
The traffic police advises members of the public who go out drinking to consider other options such as using a valet service, taking public transport or designating a non-drinking driver.
The penalty for drink driving is disqualification from driving for at least a year. First-time offenders can be fined between $1,000 and $5,000, or jailed up to six months. Repeat offenders can be fined up to $30,000 and jailed up to three years.