Lane sharing/splitting/straddling
 

I appreciate any comments, suggestions, and questions.The whole area of lane sharing/splitting can be confusing, particularly in terms of when/where it's legal, safe and appropriate. This writeup attempts to explain the concepts and issues as simply and clearly as possible.

Basic definitions.
Various people use the following terms in various ways, sometimes interchangeably. I've tried to sort it out by what most people mean most of the time.

• Lane-sharing: (or sharing lanes). The practice of traveling far enough over to one side or another of a lane to leave room for the driver of another vehicle to also use part of that same lane (to be overtaken, or to share side-by-side at the same speed), or the practice of using unused space in a lane to overtake slower traffic using another part of that lane. Motorcyclists sometimes share lanes not side-by-side, but in a staggered fashion - one ahead and over laterally from the other. Dozens of bicyclists sometimes share one lane by riding in tight packs behaving like a single unit, similar to a flock of birds.
• Lane-straddling: Operating a vehicle on or near a lane stripe that separates two lanes such that the vehicle is encroaching at least some into both of the adjacent lanes separated by the stripe.
• Lane-splitting: The practice of sharing lanes by riding a bicycle or motorcycle between two lines of traffic. Note that passing a line of congested traffic on the outside is not "lane-splitting", because the cyclist is not between two lines of traffic.
• Whitelining: Using lane-straddling in order to lane-split.
• Controlling the lane: Cycling in a lane position that precludes others (particularly drivers of cars and other 4-wheeled vehicles) from using adjacent space within the same lane at the same time. Commonly referred to as taking the lane. If a cyclist is controlling the lane then he is not lane-sharing (and vice-versa).
• Filtering forward: Using lane-sharing (either on the outside or lane-splitting) to overtake slow or stopped traffic.

Some observations that stem from these definitions:

• Lane-splitting comes in two basic varieties:
  1. Whitelining -- splitting the two lanes at or near the white lane stripe: riding on or near enough to the stripe to be encroaching into both lanes at once;
  2. Without whitelining -- splitting the two lanes far enough over from the white lane stripe to not be encroaching into the adjacent lane: riding in a lane in the space between the lane stripe and vehicles in the same lane, but not encroaching over the center of the lane stripe into the adjacent lane.
• Lane-sharing without lane-splitting is lane-sharing on the outside (using space to the right of the rightmost lane).
• Curbhugging is extremely generous (to a fault) lane-sharing on the outside. Usually it refers to riding so far to the right that safety is unnecessarily compromised for one reason or another.
• In the context of motorcycling, lane-sharing is almost always used to refer to filtering forward while lane-splitting, so these three terms, along with whitelining, are often used interchangeably in that context. For example:
  Often called lane-splitting, white-lining, or filtering, lanesharing is the practice by motorcyclists of moving between stopped or slow moving traffic during times of congestion and between lanes of vehicles, traveling in the same direction. http://laneshare.org/index.html
  But for bicyclists, who are often moving slower than other traffic, lane-splitting is not necessarily done in order to be filtering forward, and lane-sharing is not necessarily whitelining (could be sharing on the outside, or splitting without straddling lanes), filtering forward (in fact usually the bicyclist is being overtaken), or lane-splitting (between lines of traffic)

Legal issues
Language in laws like California's CVC 21658 seem to make lane-splitting illegal, if you read it with lane-splitting in mind:

• 21658. (a) A vehicle shall be driven as nearly as practical entirely within a single lane and shall not be moved from the lane until such movement can be made with reasonable safety.

However, what this law is clearly intending to prohibit is lane-straddling by drivers of normal-width vehicles, in order to prevent one driver from occupying two lanes simultaneously. Clearly a whitelining cyclist cannot do that. If the intent was to prohibit lane-splitting, then why would they prohibit lane-splitting of the whitelining variety, but not lane-splitting of the without whitelining variety? Since they are clearly not prohibiting lane-splitting of the without whitelining variety, it seems reasonable to assume that there is no intent in 21658 to prohibit any kind of lane-splitting.

Safety issues
Just because it's legal, doesn't mean it's safe. Both varieties of lane-splitting, as well as lane-sharing on the outside, have various hazards. When traffic is stopped, riding in door zones is always hazardous, on either side. It can be the safe and reasonable thing to do when done carefully. If the reasonable safety of lane-splitting or lane-sharing is in doubt in a given situation, don't do it.


I appreciate any comments, suggestions, and questions.

EDITS:
02/01/08 - Added curbhugging definition per Bek's question.
02/02/08 Changed lane-sharing definition from:

• Lane-sharing: Traveling fully within a lane, but alongside another vehicle in that same lane. The other vehicle may be lane-sharing or lane-straddling.

to:

• Lane-sharing: Traveling fully within a lane, but far enough over to one side or another to leave room for another vehicle to travel alongside in that same lane. When another vehicle is present alongside it may be lane-sharing or lane-straddling, and may be moving faster, slower or at the same speed (traveling alongside another vehicle moving at the same speed is generally considered dangerous, whether it's the same or an adjacent lane).

02/02/08: Added controlling the lane definitions; expanded on curbhugging.
02/04/08: Updated definitions of lane-sharing and lane-splitting; added whitelining and filtering forward, etc. See post #36 for details.
02/05/08: Updated lane-sharing again. See post #40 for details.
02/05/08: Expanded the observation about the varieties of lane-splitting.

what about the curbhugging?

Curbhugging is extremely generous lane-sharing on the outside.

This thread is the biggest waste of bits and bytes ever.

Shouldn't you be riding?

How about: Riding in traffic is hazardous, so is leaving the house.

extremely generous? :roflmao: who makes that determination? You, helmet? :roflmao: what about blatant curb hugging of low speed lanes too narrow to share?

IMHO: He's like those self-proclaimed "experts" you see that rant on and on about what the rest of the established scientific community has already established false... except he's just on a bike.

In Europe it's called filtering.

what about sharing the lane to the left?

In construction zones this is very common.

Sharing the lane to the left of what?

You crack me up! You take a gray area of the law and attempt to reduce it to black and white by stating falsehoods as if they are fact and claiming that nonsense is obvious.

Your original post is so full of horse hockey I don't even know where to begin.

Mark me down as disagreeing with virtually everything you say.

Since I don't have the time to detail every point of disagreement, allow me to cherry-pick.

Because it's redundant to prohibit things that are already prohibited. I know it goes against VC-ist dogma but, as a general rule, lane-sharing is prohibited in all 50 states (with a few, explicitly stated, exceptions, such as two bicycles in the same lane)-- even in California where the CHP has said that it doesn't care what the law is, it isn't going to enforce a ban on lane-sharing unless it feels like it.

I hate to burst your bubble, but the VC-ist dogma that says that lane sharing is "vehicular" is a gigantic load of cow chips- the "WOLs are better than bike lanes" crowd notwithstanding.

WOLs are ambiguous. If I'm 11 feet over in a 18 foot lane, am I bicycling too far left for lane sharing?

How about the practice of Hair-splitting?

I just stay out of the way and never seem to piss anyone off. Well, just once, when I was taking the lane.

I completely disagree. Why wouldn't all slow moving vehicle laws simply say that the slow moving vehicle must use the rightmost lane available for through traffic? What's the purpose of the "as far right as practicable" language if not to allow for lane sharing?

This thead has nothing to do with WOLs or bike lanes.

Anyway, from the CHP website:http://www.chp.ca.gov/html/answers.html

I don't see the CHP saying it doesn't care what the law is.

Again, this thread has nothing to do with WOLs.

Anyway, the WOL is not ambiguous - your position 11 feet over (from the lane stripe on your left, I'm assuming) is what is ambiguous (with respect to whether you're sharing or controlling the lane). Would anyone ride a motorcycle in that position, especially relatively slowly to other traffic? Note that if the 18 foot lane had a 5' wide bike lane, at 11' over you'd be 2' to the left of the BL stripe, which would be 13' over.

If you want to be clearly sharing, then 11 feet over is probably a bit too far left. If you want to be controlling, 11 feet over is too far right.

Make sense?

no.

If it were true that "lane-sharing is prohibited in all 50 states ", California, the UVC and most states would not have laws that refer to lane sharing. But they do. For example:http://dmv.ca.gov/pubs/vctop/d11/vc21202.htm

The obvious implication is that a lane that is wider than a "substandard width lane" is wide enough" for a bicycle and a vehicle to travel safely side by side within the lane." And legally.

A bicycle and a vehicle traveling side by side within the lane is lane-sharing, by definition, given the way I defined it the way I did in the OP:

Now, if you want to define lane-sharing some other way, and say that is illegal, fine. But then you need to tell us how you are defining lane-sharing.

Ok, your definition of lane straddling means nothing to me, at best its redundant, its what you do when you split lanes/filtering.

Lane splitting/filtering, which is passing cars by going between two lines of cars, regardless of its legality, is something I will do in very slow traffic, but realizing that it does carry a relative amount of risk over just taking the lane and flowing with traffic, I do it very cautiously.

Your definition of lane sharing is extremely dangerous and I avoid it at all costs. Its an invitation to get right hooked or left hooked by a car. Whenever a car comes right next to me, I take immediate evasive action to either get in front of or behind the car.

It's redundant because you don't recognize lane-splitting that is accomplished without straddling two lanes, it seems.

Consider an 11 foot lane adjacent to a 16 foot lane, with traffic stopped in both lanes near the right side of their respective lanes. That leaves a wide enough space to the left of the right line of cars, but to the right of the stripe dividing the two lanes, for motorcyclists and cyclists to use to filter forward. That would be lane-splitting without lane-straddling.

One example of lane-sharing, as I defined it, is what is required by law whenever a driver of a slow moving vehicle, a right-turning driver, is required to operate "as close as practicable to the right", or when a bicyclist is required to ride "as close as practicable to the right" that is wide enough" in an outside lane that is wide enough "for a bicycle and a vehicle to travel safely side by side within the lane."

No, your definition of lane sharing is:

Lane-sharing: Traveling fully within a lane, but alongside another vehicle in that same lane. The other vehicle may be lane-sharing or lane-straddling.

And my point is riding alongside another vehicle is always one of the most dangerous things you can do on a bike.

In HH's examle, he's talking about a slow moving vehicle being alongside a faster moving vehicle. In order to be slow moving, the vehicle alongside must therefore be passing the slower vehicle. The alongside part only happens temporarily which greatly reduces the potential danger. Of course, I'm referring only to between intersections with that statement. At intersections, I would agree that it's not generally safe to be in a lane sharing position regardless of relative speeds.

Oh! I absolutely agree and realize now your point. Yes, if you're lane-sharing while moving at the same speed as the other, that's dangerous. I was taking that for granted and only thinking about lane-sharing when one is moving faster than the other and in the process of overtaking. After all, this was all written in the context of lane-splitting which is usually done when the cars are stopped. But whether they're moving at the same speed or not, it's still lane-sharing.

Anyway, I'll try to clean up the OP a bit on this point. Thanks.

Edit: This lead to the following change in the OP:

02/02/08 Changed lane-sharing definition from:

• Lane-sharing: Traveling fully within a lane, but alongside another vehicle in that same lane. The other vehicle may be lane-sharing or lane-straddling.

to:

• Lane-sharing: Traveling fully within a lane, but far enough over to one side or another to leave room for another vehicle to travel alongside in that same lane. When another vehicle is present alongside it may be lane-sharing or lane-straddling, and may be moving faster, slower or at the same speed (traveling alongside another vehicle moving at the same speed is generally considered dangerous, whether it's the same or an adjacent lane).

Better?

Exactly.

My understanding is that "filtering" is not restricted to lane-splitting, but can be done by lane-sharing on the outside as well.

I've added a definition for filtering forward to the OP.
Please let me know whether what I wrote is consistent with your understanding. Thanks.

I've also added definitions for controlling the lane and expanded on curbhugging.