California motorcycle handbook (DL 665) - download, plus the laws to study

What DL 665 is, and what this page is

The California motorcycle handbook is DL 665, published by the DMV. It comes as a PDF download in English and Spanish, and that is the only form it comes in: the department publishes the car handbook as readable online sections you can scroll through, but it has never done the same for the motorcycle one. Download DL 665 from the DMV - it is the official summary, and it is what the DMV tells riders to study.

This page is deliberately not a copy of it. DL 665 is the DMV’s own text and stays that way; what follows is written from the California Vehicle Code, the law the rules are drawn from, with every statement cited to the section that states it. The handbook condenses the code into rider-friendly guidance. The code is the operative text, it is free to read, and unlike the handbook it can be linked one section at a time - which is exactly what makes it studiable on a phone.

Two boundaries worth setting before you read on. Licensing - the instruction permit, the CMSP course, the knowledge and skills tests - is the motorcycle license guide. And lane splitting and the helmet law in depth, including where the CHP’s speed guidance fits, live on motorcycle rules of the road. This page is the study spine that points at both.

Helmets: who must wear one, and to what standard

Two sections do the work, and they do different jobs.

§27803 sets the requirement. Subdivision (a) reaches a driver and any passenger riding on a motorcycle, motor-driven cycle or motorized bicycle. There is no age threshold in the section, so it is not a rule about young riders - it applies to everyone on the machine. Subdivisions (b) and (c) make it separately unlawful both to operate and to ride as a passenger when either person is not wearing one, so the duty does not sit only with the rider in front.

The part riders miss is subdivision (e), which defines what wearing one means: a helmet on the person’s head, fastened with the helmet straps, and of a size that fits securely without excessive lateral or vertical movement. An unfastened helmet, or one too large to sit still, does not satisfy the section merely by being present.

§27802 sets the standard. It directs that the regulations include the requirements of Federal Motor Vehicle Safety Standard No. 218 (49 C.F.R. §571.218), and it requires helmets offered for sale to be conspicuously labelled in accordance with that federal standard - a label that the section says constitutes the manufacturer’s certification that the helmet conforms. Subdivision (b) makes selling a non-conforming helmet unlawful in its own right. So the familiar DOT label is not decoration: it is the certification the statute points at.

Lane use, and what lane splitting actually is

Start with the ordinary rule. §21658(a) requires that a vehicle be driven as nearly as practical entirely within a single lane, and not moved from that lane until the movement can be made with reasonable safety. That is the baseline every vehicle rides under, motorcycles included.

§21658.1 is the section people mean when they say lane splitting is legal in California, and it is worth being precise about what it actually does. Subdivision (a) defines the term: driving a motorcycle as defined in §400, with two wheels in contact with the ground, between rows of stopped or moving vehicles in the same lane, on divided and undivided roads alike. Subdivision (b) says the CHP may develop educational guidelines, and (c) lists who it consults.

What the section does not contain is an operative sentence granting permission. It defines the manoeuvre and builds a safety-guidance framework around it. California is the state that put lane splitting into its Vehicle Code by name, and the practice is lawful here because nothing prohibits it - not because §21658.1 announces that it is allowed. The distinction matters when you are studying: the definition is the examinable part, and the conditions inside it - two wheels down, between rows, within the same lane - are what mark the boundary of the term.

That definition also tells you what lane splitting is not. Riding between traffic and the edge of the road is not between rows of vehicles, and the shoulder is not a traffic lane.

The equipment the Vehicle Code requires

Four sections cover the machine itself, and three of them are routinely misremembered.

Mirrors - §26709. Subdivision (a)(1) requires every motorcycle subject to registration in California to carry a mirror positioned to show the rider the highway for at least 200 feet to the rear. Note the singular. Subdivision (a)(2) imposes the familiar two-mirror rule on every other motor vehicle and names the motorcycle as its exception. One compliant mirror is the legal minimum; a second is a good idea, not a requirement.

Headlamps - §25650.5. Every motorcycle manufactured and first registered on or after January 1, 1978 must carry at least one and not more than two headlamps that come on automatically when the engine starts and stay lit while it runs. Both halves are worth holding onto: the always-on behaviour is built into the machine by law rather than left to the rider, and the section caps the number at two.

Seat and handlebars - §27801. A two-wheel motorcycle may not be ridden if the seat is positioned so the rider cannot reach the ground with their feet when sitting astride it, or if the handlebars put the rider’s hands more than six inches above shoulder height when on the grips. The handlebar figure is the one that gets mangled in retelling - it is measured against your shoulders, not a fixed height off the road.

Exhaust - §27151. Subdivision (a) prohibits modifying a vehicle’s exhaust system so as to amplify or increase the noise beyond the limits that apply, and prohibits operating a vehicle so modified. Subdivision (b) is the trap: it offers a 95 dbA allowance for vehicles under 6,000 pounds gross vehicle weight rating, and then excludes “other than motorcycles” from it by name. Quoting 95 dbA as a motorcycle limit reverses what the statute says.

Carrying a passenger

§27800 is short and specific. A rider may not carry another person on a motorcycle or motorized bicycle except on a seat securely fastened to the machine behind the rider and provided with footrests, or in a sidecar attached and designed to carry a passenger. The final sentence puts a duty on the passenger too: feet on the footrests while the vehicle is in motion.

Read alongside §27803, that gives you the full passenger picture - a proper seat, footrests, feet on them, and a fastened helmet that fits. Note also that an instruction permit carries its own passenger restriction, which is covered on the motorcycle license guide rather than here.

What riders most often get wrong

These are the four the sections above contradict outright, gathered in one place because they are the ones worth arriving at the test already knowing.

• “Two mirrors are required.” The opposite: §26709(a)(2) names motorcycles as the exception to the two-mirror rule. One mirror showing 200 feet to the rear is the minimum.
• “95 decibels is the motorcycle limit.” §27151(b) excludes motorcycles from that allowance in its own text.
• “Handlebars can’t be above your head.” The measurement in §27801(b) is your hands on the grips versus your shoulder height, and the figure is six inches.
• “Adults can ride without a helmet.” §27803 has no age exemption at all. Its one exemption, in subdivision (f), describes a fully enclosed three-wheeled vehicle of a specified size and weight.

When the code and a half-remembered rule disagree, the code is the one the DMV, law enforcement and the courts work from. Every section above is linked in the sources below, so you can read the operative text rather than take this page’s word for it.