With traffic law we have a situation in this country where traffic law (non criminal) can overlap into traffic law (criminal) and the range of offences that fall in between are wide and varied.
So, a quick history lesson.
Back in the day when I first entered policing, section 1 of the Road Traffic Act 1972 was causing death by reckless driving with section 2 being reckless driving.
Very few drivers were ever convicted under this section because you had to prove a state of mind. So I would interview a driver I had arrested after a fatal crash any my question would be along the lines of
"Were you aware of the possible consequences of your actions as you carried them out?" As soon as the defendant replied "No" your section 1 or section 2 went straight out of the window and you were only left with the lesser offence of a section 3, careless driving which is sub divided into Driving without due care and attention, and driving without reasonable consideration for other road users, hence the reasoning behind a lot of plea bargaining.
But in 1988 with the introduction of the current road traffic act, Reckless was changed to dangerous and suddenly things changed because all we have to do to get a conviction for death by dangerous or dangerous driving is show that the standard of driving fell well below the standard expected of a reasonably safe and competent driver. The burden of proof was easier to establish and we were no longer reliant on proving a state of mind.
But we do then get offences which are strict liability as mentioned
Speeding
Tailgating.
Centre lane hogging (careless driving)
Failing to conform to an obligatory traffic sign such as a stop or give way, and so the list goes on.
Most construction and use offences are strict liability (although there a few statutory defences such as the ABS failing during a journey) but driving with a defect or failing to maintain are again strict liability hence the need to keep the vehicle up to standard.
But then we have the other side of the coin where unlike say the Theft act of 1968 where very little has been changed over the years, traffic law changes almost daily and so it is sometimes difficult for the average motorists to keep on top of things.
This is where a bit of discretion by the Police/prosecution can be allowed because clearly nobody can know every traffic law (I had to do a 12 week traffic law course which was longer than my basic training, and if any one of us got less than 80% on our weekly exam, the following day we would be back walking the streets with a tall hat on our heads)
But even with the ever changing law, the average driver knows the difference between driving reasonably and (excuse my language) taking the p*ss, and if he drives in a reasonable manner then he/she will be left alone.
But in the same vein traffic police these days do not get the training that I was fortunate to receive back in the day (budget cuts) and so many of them do not know the rules that govern the road, but we do get a lot of bar room lawyers who will argue black is white that they are right and everyone else is wrong mainly caused by the internet.
The other problem is that there are so many laws and regulations.
The Road Traffic Act
Construction and Use Regulations
Road vehicle lighting regs
Driving licence regs.
HGV/PCV regs
Road Traffic Regulations Act.
Motorway Regulations
Highways Act
To name but a few....
Give you another example......
A year or so ago I had gone down to Gloucester where I was guest speaker with an advanced driving group.
I departed the venue after 11pm and was winding my way home up the M4 when I had a car sat in lane 2 of a near empty Motorway doing about 55 and another vehicle in lane 3 doing around 60.
I went past on the nearside of the lane 2 hogger at 70 and about half a mile up the road on go a set of blue lights and I am pulled in by the local motorway traffic cop.
He got out of his vehicle and was ranting and raving and telling me how he was going to throw the book at me for undertaking, so when I asked him what specific offence he was going to report me for he suddenly looked puzzled.
I asked him to book me as I was going to have great joy in going to court with a not guilty plea and then claiming costs against Police because he could not establish I had committed any offence.
His answer was undertaking was an offence, so I asked him to quote act and section and then pointed out the specific offence was removed in the 72 road traffic act, and that only left careless and then he would have to prove that my driving fell below the standard of a reasonably safe and competent driver and the simple act of undertaking was insufficient especially when the driver in the middle lane was guilty of a strict liability offence.
He was working on the Highway Code rule which states should not, it does not say MUST not. Had it been a must not it would have been qualified by the appropriate act and section, but he did not know that.
Anyway, long story short, he asked me how I knew all this and then saw my IPA (International Police Association ) badge in the windscreen and asked if I happened to be traffic or road policing by any chance? He was not a happy chappy when we parted, and I would have hated to have been in the shoes of the first driver he stopped after stopping me.
But therein lies much of the problem. Laws change regularly, traffic police are not experienced or qualified as they should be, but the public are non the wiser and I have often wondered how many have been prosecuted when it did not even warrant a booking in the first place.
Sorry I have rambled on, but it is not a question that can be given a simple answer as there are so many issues.
But.....As one of my old law instructors once said, "The best guide is, if it feels wrong, it usually is wrong" hence the reason who some drivers are reported for any offences that may be disclosed which is cop speak for "I need to go away and think about this and maybe look it up.