You see it all the time on the road - drivers turning or changing lane without signalling their intention to do so.
But according to traffic rules, the failure to signal is an offence.
The Traffic Police said 564 summonses were issued for this in the first six months of this year - the highest in three years. The penalty, according to the Traffic Police, is a $70 fine for light vehicles and a $100 fine for heavy ones.
But many motorists told The Straits Times that they did not know they could be fined for turning without signalling.
Retiree Thomas Wee said: "I didn't know that. So many drivers are not doing it."
Mr Wee, who is in his 60s and has been driving for about 40 years, asked: "Why then are they getting away with it?"
Freelance writer Kevin Chin, 33, who drives and rides a motorcycle as well, said he is aware of the rule, "although I haven't met anyone who's been caught".
That could be because the number of summonses issued for the offence pales in comparison to those handed out for better- known infringements such as speeding and running red lights. These made up the bulk of the 367,496 traffic violations last year.
Like turning without signalling, other practices that irk motorists make up a small percentage of total traffic infringements.
For instance, driving without lights on and road hogging - defined as the obstruction of traffic moving at faster speeds.
The Traffic Police said 603 summonses were issued for road hogging in the first half of this year and 72 for driving without headlights on between 7pm and 7am. They attract fines of $70 and $30 respectively.
Another little-known offence is failing to be in the right lane before making a turn at a junction.
For instance: a driver who wants to turn right, but remains on a straight-moving lane and causes obstruction to other motorists who want to go straight ahead. The penalty for this is a $130 fine and four demerit points for light vehicles, and a $160 fine and four demerit points for heavy vehicles.
Mr Gopinath Menon, vice-chairman of the Singapore Road Safety Council, attributes the "general lack of road courtesy" to "everyday pressures".
"Everybody is in a hurry," he observed. "And there has been more traffic on the road in recent years."
Automobile Association of Singapore chief executive Lee Wai Mun blames "social norms".
He said turning without signalling is not common in many Western countries "because of societal pressure". In other words, the practice is frowned upon. But in Singapore, Mr Lee added, "when you signal to filter, someone from behind rushes in to fill the gap".
He believes the trend can be reversed with a mix of "education and enforcement".
"The two must go hand in hand," he said. "It takes time and effort, but if we can do it, everyone will be better off."
For a complete list of traffic offences that attract demerit points, go to http://driving-in-singapore.spf.gov.sg/services/driving_in_singapore/ser...