What do you call someone who commits a traffic violation?

I'd suggest, minor offender.

minor offense: noun A criminal infraction less serious than a misdemeanor. These infractions may not even be tracked as part of a criminal record, depending on state and local laws. Generally, these types of infractions carry penalties of monetary fines and/or up to 90 days in jail. Depending on the state and local statutes, an example of a minor offense is a parking violation or traffic (driving) offense. YourDictionary

In light of your edit, consider [minor] traffic scofflaw.

scofflaw:

One who habitually violates laws, especially laws that do not involve serious criminal offenses. AHD

A contemptuous law violator M-W

Traffic scofflaws run the risk of getting ticketed, or even losing their license, because they constantly ignore traffic laws.

You could consider using habitual traffic offender for someone who habitually commits those violations you mentioned. According to Washington State Department of Licensing (reference is not available on California DMV), it is defined as:

A driver who, within a 5-year period, has been:

Convicted of 3 or more offenses listed in RCW 46.65.020(1).

or

Found to have been convicted of or committed 20 or more moving violations listed in WAC 308-104-160. The violations must have occurred within a 5-year period. If more than 1 of these offenses are committed within a 6-hour period, they’re only counted as 1 on the first occasion.

The Law Place defines it as:

... and receiving 15 or more moving violations within five years.

Moving violations:

A moving violation is any violation of the law committed by the driver of a vehicle while it is in motion. The term "motion" distinguishes it from other motor vehicle violations, such as paperwork violations (which include violations involving automobile insurance, registration and inspection), parking violations, or equipment violations.

[Wikipedia]

You may call this person a misdemeanant. Definition:

A person convicted of a misdemeanor or guilty of misconduct.

Definition of misdemeanor:

A minor wrongdoing.

You may also call this person an infractor. Definition:

One that infracts or infringes: violator, lawbreaker

(Oxford Dictionaries Online: misdemeanant, misdemeanor)

(Merriam-Webster: infractor)

I would suggest the term transgressor

Examples from the net

• The fliers also list how much a transgressor would have to pay if ticketed, and warn that real tickets will be passed out in the future if parking laws continue to be ignored,...

• Whether a frequent offender or occasional transgressor, parking fines can be paid easily through Ticketzen, a mobile app that only requires motorists to scan a ticket bar code to pay it off via credit or debit card.

• Third Stage: If 24 and 34 points are accumulated, the transgressor is required to attend a special course on driver safety.

• Red-faced officials from the department of justice and the department of transport are working to scrap the amendment in the Criminal Procedure Act, which stipulates that a traffic officer can arrest a road transgressor only after getting the go-ahead from a magistrate.

• Edinburgh City Council must back up its rhetoric and ensure all companies are aware of their obligations and to use every power available to name and shame them and maximise the fines for transgressors.

If the infraction involves flouting the speed limit, the driver can be called a speeding motorist

If the transgressor is a repeat offender then I would suggest the following:

1. Regular transgressors run the risk of getting ticketed, or even losing their licence, because they constantly ignore traffic laws.

2. Having more police on the roads, stopping and awarding black points to those who break the rules, will force repeat transgressors to rethink their behaviour.

3. Frequent transgressors who park in residential area are first made aware of their obligations and asked to move. Ultimately they can be reported to the Traffic Commissioner who can revoke their licence.

4. Repeat offenders run the risk of getting ticketed, or even losing their licence, because they constantly ignore traffic laws.