I don't think I've ever understood this.

I travel frequently across the State of California by car. And I often take the highway to get to many places.

One thing I don't understand is how fast lanes and slow lanes work. I was recently travelling on a fast lane near San Francisco driving at the speed limit, when I noticed a cop who was travelling behind me honk at me, presumably because I was going slowly? I noticed there was a long line of cars behind me.

So I moved into the slow lane. But even weirder is that cars in the slow lane drive at the speed limit, and cars that drive in the fast lane drive way past the speed limit, even cops. And I have never seen anybody get arrested for going faster than the speed limit, except for really fast drivers.

So I don't understand, even with 6 years of driving throughout California under my belt. I understand the fast lane is for fast cars, but doesn't driving at the speed limit constitute fast? I really don't understand. I talked to a local officer and they said that if there are cars tailgating you or lining up behind you, you should change lanes to a slower one, but if I'm already driving at the speed limit, how can I go any faster?

  • 8
    This site is about travel in the sense of going to remote places. It's not really about driving. Commented Sep 17, 2014 at 2:26
  • 4
    This question appears to be off-topic because it is about driving. Commented Sep 17, 2014 at 2:27
  • 16
    @DJClayworth How can "driving" be off-topic if it has existed as a tag and has 144 questions linked to it?
    – yuritsuki
    Commented Sep 17, 2014 at 2:39
  • 22
    @DJClayworth Obscure local customs that are relevant yet surprising to travellers, like police officers telling you to exceed the posted speed limit, are perfectly on-topic for a travel site. Commented Sep 17, 2014 at 3:26
  • 10
    unshakeable - you seem to be one of these folks who think you have the "right" to travel in the fast lane, just because you're sitting on the speed limit. OK, so you are wrong. Make this QA an opportunity to get the wrong idea out of your head. As is explained below, the law 21654-A tells you what to do. Obey the law. Couldn't be simpler. Note that on the road one should obey laws .. not "feelings" one may have about what is "right and wrong", you know? Follow the law .. 21654-A !!
    – Fattie
    Commented Jun 9, 2016 at 14:26

9 Answers 9


To vastly overgeneralize, most people consider posted speed limits in the United States to be too slow. All things being equal (good weather etc), it's expected that you drive about 10 mph over the speed limit, and police generally ignore people who do.

In a few states, notably Texas, this is enshrined in law, and you can exceed the speed limit and potentially get away with it even in court as long as you can make a good case that it was "reasonable and prudent" to do so. In most states, though -- and this includes California -- the letter of the law says that exceeding the posted speed limit is always illegal.

So what to do? The Solomon curve states that the safest speed to drive is at the average speed of traffic or slightly higher. So if you're driving the speed limit, and everybody else is speeding (slightly), you're actually exposing yourself and everybody else to a greater risk of crashing. Better to stay with the flow and speed slightly: as long as "everybody else is doing it", you will stay safer and most likely get away with it. Or, if you're not comfortable doing this, then stick to the slow lane and drive the limit.

  • 6
    California actually has a "Reasonable and Prudent" standard in it's law. However, proving that anything over the posted limit is reasonable and prudent is next to impossible, so it's something of a moot point. Commented Sep 17, 2014 at 4:08
  • 5
    @LessPop_MoreFizz: AFAIK "Reasonable and Prudent" is there for the sake of case, when you have lets say highway with 65mph speed limit, but there's a intense snowstorm. In that case it would be unreasonable and imprudent to drive at 65mph, even though it's within the speed limit.
    – vartec
    Commented Sep 19, 2014 at 14:59
  • 3
    It's not difficult at all to prove that something over the speed limit is reasonable or prudent. Say, for instance, you see a semi start to swerve into your lane and your closest path out of his way is to just accelerate. It would be hard to argue that that is not reasonable and prudent. Furthermore, anyone that has driven on I-75 through downtown Atlanta can tell you that, under normal conditions, driving less than 10-15 mph above the speed limit is decidedly unsafe, due to the flow of traffic. When traffic is doing 80, it's quite reasonable and prudent to drive above 55.
    – reirab
    Commented Dec 22, 2014 at 22:28
  • 7
    Having said that, I would strongly disagree with the assertion in the answer that it's expected that you drive about 10 mph over the speed limit. This is extremely location dependent. In Georgia (outside of Atlanta,) that's normal. On rural areas of the Interstates in Tennessee, though, 10 over is not at all normal and is borderline on what will get you a ticket. In other places, 10 over will definitely get you a ticket. The best general rule of thumb is to follow the flow of traffic or, when there isn't other traffic, stay close to the limit.
    – reirab
    Commented Dec 22, 2014 at 22:33
  • 3
    @Andy: Done. And I still don't see what you see. In fact, the wikipedia article even makes the explicit point that the 85th percentile standard can lead to speed limits that are too high.
    – user24581
    Commented Dec 26, 2014 at 1:37

As far as I can see, Vehicle Code of California states, that you should in fact keep right.

V C Section 21654 Slow Moving Vehicles

Slow-Moving Vehicles

  1. (a) Notwithstanding the prima facie speed limits, any vehicle proceeding upon a highway at a speed less than the normal speed of traffic moving in the same direction at such time shall be driven in the right-hand lane for traffic or as close as practicable to the right-hand edge or curb, except when overtaking and passing another vehicle proceeding in the same direction or when preparing for a left turn at an intersection or into a private road or driveway.

(b) If a vehicle is being driven at a speed less than the normal speed of traffic moving in the same direction at such time, and is not being driven in the right-hand lane for traffic or as close as practicable to the right-hand edge or curb, it shall constitute prima facie evidence that the driver is operating the vehicle in violation of subdivision (a) of this section.

(c) The Department of Transportation, with respect to state highways, and local authorities, with respect to highways under their jurisdiction, may place and maintain upon highways official signs directing slow-moving traffic to use the right-hand traffic lane except when overtaking and passing another vehicle or preparing for a left turn.

  • 7
    Clearly the only correct answer. In any case my experience driving in California (mostly Southern California) has been that drivers will expect you to behave this way. Slower traffic should keep right unless you're passing. Commented Dec 23, 2014 at 23:45
  • 2
    Indeed, the straightforwardly correct answer. It's a law, 21654-A.
    – Fattie
    Commented Jun 9, 2016 at 14:24

Generally speaking there is no Fast and Slow lanes on most highways in California or any other state for that matter unless specifically indicated by the lane speed limit, if you're referring to driving in the left lane on a multi-lane highway it doesn't necessarily mean that you will or should be driving faster than the one on the right.

There is a law in California and most other states regarding driving at such a slow speed that it impedes traffic, so if you have created a caravan of cars behind you like in the case of the police officer honking at you you probably were impeding traffic.

In addition to that you should watch for police and other emergency vehicles on the road because even if they do not run with the flashing lights you should give them the right of way unless you're unable to do so.

Now for the last point unlike Europe and a lot of countries outside the US on a multi lane highway in most states it is legal to pass on the right specifically so that the traffic creators, like you were in that case, can be overtaken.

Now as far as Speed Limits are concerned the enforcement and legality of exceeding the speed limit is determined by the state and in quite a few jurisdictions exceeding a posted speed on a highway by no more then 10 mph even, though it may technically be illegal will not cause you to be stopped by Police (too much work for little reward) and this fact is taken advantage of quite frequently by people.

  • But that's the thing, I was driving at the speed limit, which is considered the "maximum speed on the road". So if I were to be in the fast lane, why would I need to move into another lane?
    – yuritsuki
    Commented Sep 17, 2014 at 17:25
  • 5
    @thinlyveiledquestionmark Because other traffic is moving faster. Legally you didn't need to move over but again you are moving slower then the rest of the traffic, so you were technically impeding traffic so if a police officer wanted to cite he would have. Generally speaking from experience most people driving in the left lane exceed speed limit to a varying degree and it is extremely annoying when a slow moving vehicle is making movement difficult.
    – Karlson
    Commented Sep 17, 2014 at 18:03
  • 3
    @thinlyveiledquestionmark if everyone is speeding but you, you're still impeding traffic. Nothing about that law says "unless traffic is speeding ".
    – Andy
    Commented May 23, 2015 at 0:59
  • 1
    @thinlyveiledquestionmark You can move to the right lane. Also, 85% of speed limits in the US are 8-12 MPH below what they should be according to engineering studies (google 85% percentile rule). Slower != safer, and if you're impeding the flow of traffic that actually increases the risk of an accident, even if you're above the speed limit. And lets be honest, speed limits are set to generate revenue for the localities, they aren't set to be safe.
    – Andy
    Commented May 26, 2015 at 12:28
  • 6
    @thinlyveiledquestionmark I'm not sure about CA specifically, but in many, if not most, U.S. states, you actually are required to move over, even if you're going the speed limit. In some states, you're legally required to drive in the right lane unless you're actively overtaking someone. In other states, you're legally required to get out of the way of people driving faster than you when possible (i.e. whenever you're not actively overtaking someone.) Also, driving right beside another car in the lane beside you is both dangerous and illegal. In VA, it's automatic reckless driving.
    – reirab
    Commented Jul 2, 2015 at 2:41

Almost every state, if not every state, in the U.S. has a law that says that slower traffic should keep to the right lane(s) on multi-lane highways. In some states, the left-most lane(s) are considered passing lanes only and all traffic is supposed to stay to the right when not actively overtaking other traffic. This prevents exactly the situation that you found yourself in with traffic backed up behind you. Regardless of whether you're driving the speed limit, backing up traffic is dangerous and, in many places, illegal. In some states, you can even be cited for reckless driving for such behavior (even if you're going the speed limit.) So, in summary:

1) Please drive around the same speed as the rest of traffic where it is reasonably safe to do so (just don't drive right beside someone else doing the same speed when it can be avoided.)

2) When you must drive at a speed below the general flow of traffic, stay as far to the right as possible and only move to the left when you need to pass someone or to make room for someone to merge in from an on-ramp.


In my opinion in general it is best to drive on the slowest lane possible with your desired speed, i.e. if the slow lane is moving at the speed limit then just drive there. In many European countries this is actually illegal to drive on the faster lane if there is space on the slower lane (e.g. Germany). This way you are not blocking people who want to drive faster, whether they are breaking the law or not.

As many other people already said, in some areas it is "customary" to exceed the speed limit slightely, so most often clogging the fast lane just because you drive at the speed limit is not considerate to the other drivers.

  • 3
    In many European countries this is actually illegal to drive on the faster lane if there is space on the slower lane (e.g. Germany). The same is true in most or all states in the U.S., but it's not enforced as much as it should be.
    – reirab
    Commented Dec 26, 2014 at 14:44

The law http://www.leginfo.ca.gov/cgi-bin/displaycode?section=veh&group=21001-22000&file=21650-21664 in California states as answered above, that, regardless of the posted speed limit, one must always be in one of the right lanes EXCEPT to pass slower moving traffic, or if there is no space whatsoever on the right due to traffic congestion. Occupying the furthest left lane (closest to the divider) is expressly forbidden regardless of speed, if other lanes are available to the right, and especially if traffic is piling up behind.

  • 1
    You are mis-reading this section of the code. This is referring to the fact that on a two-lane road you must drive on the right-hand side of the road. It explicitly states that it does not apply "(d) Upon a roadway restricted to one-way traffic.", which is normally going to be the case for highways which are one-way on either side of some form of divider. California law does NOT generally require you to drive in the right-hand most lane as in some other countries, and in fact the driving handbook recommends against driving in the far right-hand lane on multi-lane highways in many cases.
    – Doc
    Commented May 22, 2015 at 6:17
  • 3
    @Doc actually you are not reading it correctly. For example, 21654 b does apply, as do several other paragraphs. The paragraph I believe you are referring to is only referring to one-way streets, not two-way divided highways. A two-way divided highway is just that, a two-way road, with a divider (barriers or median) between the directional travel lanes; NOT two one way roads.
    – CGCampbell
    Commented May 22, 2015 at 12:40
  • @CGCampbell go on and read 21651 which talks about a truly divided highway. That is, there is at least 2 feet gap between the directions delineated by double yellow lines or a median or a barrier. That implies to me that 21650 is talking about undivided highways. So 21650 c means one direction of a divided highway. Appears to be backed up by 21659.
    – mkennedy
    Commented May 22, 2015 at 20:36

In California, as in most places in the US, the posted speed limit is more akin to the average speed of traffic than to the maximum speed of traffic; this often confuses travelers from other countries. (On many roads nearly all cars will be technically breaking the law.)

In at least one state, at one time, when new roads were built, they were left with no posted speed limit for a few weeks, and the average speed of traffic was used to set the speed limit.

It used to be relatively common knowledge that the standard highway speed varied from state to state along with traffic enforcement patterns, but there was no state where it was not a positive delta above the posted speed limit.

The general rule of thumb on multilane roads is that the further you are to the left, the faster the speed of traffic; if cars are piling up behind you or passing you on the right you should move over to a lane further to the right. (On single lane roads, if you are driving slowly enough that cars are piling up behind you, it is polite to pull over to let the traffic pass. Some roads have pullouts that can be used for this purpose.)

If you have been driving in California for 6 years and not figured this out already then you may want to reconsider whether you are attentive enough to traffic patterns to drive safely on major roads.

As a bit of related trivia, a few decades ago the police in Maryland became unhappy with the state of their union contract negotiations and organized "rolling roadblocks" where groups of police cars drove the speed limit on major highways; while they left the furthest lane open, cars were hesitant to pass them, so traffic piled up for miles behind them. (The police claimed publicly that they were concerned about the safety and federal highway funding implications of habitual speeding, but when the union contract was signed, the roadblocks stopped immediately, as did the ten-mile-long traffic jams.)

  • Erm, what. The Maryland rolling roadblock was used because the police got concerned about everyone speeding. csmonitor.com/1985/0710/aroll.html This article also mentions that some federal highway assistance could be forfeit if more than 50% of the drivers are speeding. I would exercise extreme caution before running with the advice in this answer.
    – user4188
    Commented Mar 28, 2017 at 13:05
  • 1
    @chx The part about moving to the right if there's traffic behind you is correct, though. It's the right thing to do in every state and required by law in at least several. This is true regardless of what speed you're driving. Driving the speed limit (or even above it) is no excuse to camp out in the left lane. The federal national speed limit law that that article is referring to was repealed decades ago. It was a Carter-fuel-crisis era law.
    – reirab
    Commented Mar 28, 2017 at 15:25
  • 3
    @chx when the union negotiations were going poorly the police claimed to be concerned about safety and instituted rolling roadblocks. When the contract was signed the roadblocks stopped. Complete coincidence I'm sure.
    – arp
    Commented Mar 28, 2017 at 16:47

Treat the far left lane as the 'fast/passing' lane. Meaning you are traveling in a two lane highway. Your in the far right / slow lane, you approach a car who is going excruciatingly slow and you wish to pass. Hop over to the 'fast/passing' lane to go around the driver, once passed return to the right lane.

Almost all drivers in the bay or south county do not respect the fast / passing lane, you are never to just sit cruising in the 'fast/passing' lane, the name its self is self explanatory. In California you are not to pass in the far right / slow lane, but in majority cases you have to because of drivers not following the rules of the road.

Another thing is side by side driving, just DO NOT ever ever ever do this. You are in right lane, you approach a vehicle going slow, you then move to left lane to pass BUT decide to go the same exact speed with vehicle to the side of you. Both of you are 'impeding/blocking' traffic, not allowing any one to pass on either side. People that do this cause road rage, if I come behind side by side drivers or people cruising in the fast lane, I lay on the horn. The roads are for traveling/commuting. Do not block or clog the road ways, we all need to be somewhere.

  • Comment/criticism
    – VMAtm
    Commented Apr 17, 2017 at 17:19
  • Hi Jonathan, welcome to Travel StackExchange! One thing to note when writing an answer is that the site supports using italics or bolded text for emphasis. Beside the answer entry box is a "how to format" section that explains how to do this in the text. You can also set text to be bolded or italicized by clicking the 'B' or 'I' button above the text box where the answer is entered. In general, it's better to use one of these rather than all caps for emphasis. For more information, please see How to Answer and the help center.
    – reirab
    Commented Apr 17, 2017 at 21:39
  • 1
    Side by side driving, or as the Germans call it, Elefantenrennen.
    – gerrit
    Commented Jul 4, 2019 at 8:49

I have always lived in CA, and if you ask me, this whole speed limit fast lane is BS, Myself and many others have been pulled over for going 10 miles over the speed limit while traveling in the "fast" lane. Dont believe it, they need you to go faster than the speed limit just to make their quota. Trust me, drive 65, or whatever the speed limit is, and stay out of the "questionable" fast lane, and let all those morons who think its safe to go faster than the limit posted to get pulled over.

  • 1
    This is very bad advice in some parts of the U.S. In Atlanta, for instance, it is extremely dangerous to drive the speed limit on the Interstates, since most traffic is doing 15-30 mph above it (speed limit is 55, traffic is doing 70-85, usually on the higher end of that.) You should always try to stay with the general flow of traffic, regardless of where you are in the U.S. If they pull you over for following the general flow of traffic, you'd likely beat the ticket in court, though most police won't do that in the first place.
    – reirab
    Commented Jul 2, 2015 at 2:45

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .