JohnBrooking

There's always a lot of talk here about how wide a travel lane is, and whether it can be safely shared, but I've realized recently that I really don't know how wide the lanes on the roads that I use are, in terms of a number. I can gauge roughly how shareable they are, but I have no idea the actual number of feet wide they are. Can some of you really tell that without taking a tape measure to them? Is it something you get a feel for after so many years of experience? (I've only been riding in traffic for 6 1/2 years.)

ChipSeal

Ha! I always knew about how wide they were. I would imagine laying down across the lane with my feet at the left edge and estimate where my head would be. Most lanes around here were about standard width.

One day I decided to apply a tape measure just to check. Either the tape was using extra long inches or I had been way off.

I am much better in my estimations now, but it took actually using a tape measure to get close to reality.

CB HI

I can definitely tell the difference between a 10 foot lane, a 14 foot lane and a 20 foot lane.

degnaw

I can tell the difference between a really narrow lane (two semis can't pass), a narrow lane, a normal lane, and a wide lane, all based on seeing how much of the lane motor vehicles are taking up. Foot wise, however, I have no clue.

fordmanvt

I believe the standard width is 22 feet from white line to white line. Anything past the white line is considered the shoulder.

Bekologist

Im with CBHI on this one;

to me, only at about 18 feet and over do lanes truly begin to feel equitably shareable between my bike and the cars wizzing by..

CommuterRun

Some time ago I measured some of the lanes in my area to see how wide a lane really is. They range from 9-12' depending on which road it is. All substandard width. One has a 1' paved shoulder for part of it's length, but that is so narrow I disregard that the shoulder is even there. A few, the most recently resurfaced state highways, have at least 3' paved shoulders.

For me a 14' lane would be comfortably shareable with most other vehicles. A 16' lane would be shareable with all other vehicles.

After doing this I can now look at a narrow lane and know the width. Wider lanes maybe not, but I don't think that's so important. To me if it's wide enough to share, it doesn't matter if the lane is 16' or 18 or more feet wide.

One thing I have seen that I regard as a bigger hazard than same direction traffic passing me is an on-coming vehicle passing another on-coming vehicle as they are approaching and passing me. It would take either very wide lanes or multiple same direction lanes to accommodate this maneuver safely. In this scenario a motor vehicle approaching from the rear can be used as a blocker. In the absence of same direction traffic, taking the middle of the lane in the presence of on-coming traffic mitigates this. This in one of the reasons that I believe that the best infrastructure for cyclists is narrow, multiple, same direction lanes, with signage and sharrows that give the cyclist the entire right lane.

A side note: Even though a narrow lane is easily shareable with another two wheeled vehicle, most motorcyclists in this area will change lanes to pass. I don't know why that is. If the situation were reversed, I probably wouldn't.

JohnBrooking

On another thread yesterday, someone was adding up the numbers to arrive at a safe lane width mathematically, which is what made me realize I wouldn't know anyway. My own math would go that a bike probably takes up 3' of space on the side of the road (tire tracking 2' from the usable edge, and the left side of the bike and rider is another 1' beyond that), then 3' for safe passing = 6' already gone. Someone was using 7' for a standard motor vehicle width; I don't know much about that either. But assuming that, that gives 13' as the absolute minimum shareable width.

Bek, 18' means they could give you up to 8' of passing space! However, another factor that might play into that is that I think there is a subconscious tendency in all drivers, motor and otherwise, to want to occupy the exact middle of the available space they have, rather than to one side or another of it. It makes sense that you would want to give yourself an equal buffer on both sides. This means that a motorist might not even take all the room that they have available on their left, so just to say they have N' of space doesn't mean that they'll necessarily take it. They may just take N/2' of it.

CommuterRun

That goes along with what I have found in that the more space I keep on my right, up to a point, the more room I tend to be given on my left by passing drivers regardless where the middle line is. But I think you are correct, John, in that if a motorist is given a certain amount of space in which to pass without going over the line; they are going to use the middle of that.

Road Fan

Just to cement my position as a lifelong geek, I have been studying line width, in line with my work to design a camera system that can detect lane boundaries and a car's position in the lane (it works, but ours is not timed with the car market). There's a national guideline for highway geometry design, published by AASHTO. It's not a regulation (many European nations and Japan have national REQUIREMENTS for new design, not guidelines), but I've spoken to state highway design engineers from a few states, and they say it's taken as the standard all over the US, but in many situations designs deviate. The minimum width it recommends for arterials is 10 feet. Some cities have historic roads that are 9 feet, and will not be changed. In Chicago there are several, and I rode on them as a kid, and it was scary.

Width is generally a function of curvature and of speed. For straight roads at 70 mph, the standard is 14 feet in the US. 55 mph roads are definitely narrower by design. A study took an inventory across a number of states, and found this was widely followed, up to (if I recall) 90%. Tight curves on mountain roads are usually much wider to give room for heavy trucks to negotiate the road with trailer.

Ann Arbor has lately added some BOLs to urban arterials, and left about 4 feet for bikes and 10 or 11 feet for cars.

AASHTO (American Association of State Highway Transportation Officials) has a website and publishes a set of handbooks. One of them is about design of bicycle facilities, and if they have studied lane width for truck/bike safety, I think there will be a guideline in that book. Whoever is looking at it here, it would be worthwhile to take a look at what the pro's have done, and why they've done it.

Widening lanes is a seen as a very large expense. Road authorities usually have budget identified for specific purposes, and widening is not a common one. Lining, maintainance, curb curving, and signage improvement, and signal improvement are much more common. In some cases adding width requires buying new land. NOT shovel-ready!

For context, the width of a common family sedan (2007 Accord) is about 1.8 meters (5.9 feet), the spec width of a very large American light vehicle (Ford spec) is 2.05 m (6.7 feet) not including mirrors, and very large heavy trucks can be around 2.6 m (8.5 feet) wide and still be legal. Heavy trucks are not legally permitted on the narrow Chicago roads I mentioned.

genec

Trailers can be a maximum width of 8.5 feet. That too needs to be factored in... as a truck may be narrower; it may be towing a trailer that is wider and uses more road space... AND the driver may not always consider the trailer while driving in familiar territory.

John E

It's all about relative speed. At 25mph/40kph, a 13-foot/4-meter lane is arguably just barely wide enough for sharing, but at twice that speed, I would want significantly more width.

commuterBOBbie

I tell students to look at a car in the lane, if it looks like 2 medium-sized cars (or small SUVs) can be side-by-side in the lane, it's probably a 14 foot lane.

I think you do develop an ability to recognized lane widths after a while. I had an advantage in that our bike-ped coordinator made a google earth file showing all the wide lanes.

Another thought. When I rode closer to the edge of the road, 12 foot lanes looked really wide to me. It's interesting how that perspective changes as you move toward the center.

Genec posted about trailer widths. I think trailers are a compelling reason to avoid sharing lanes... and why we should not be mandated by law to share any lane. I'm trying to organize a photo shoot with various widths of vehicles in various lanes. I think it might be an eye-opener for some cyclists to see the difference how much lane is available beside a volkswagon vs a utility trailer.

CommuterRun

If trailer width is going to be considered to be a factor; FL also has a maximum trailer width of 102" (8.5'), but "The total outside width of a noncommercial travel trailer, camping trailer, truck camper, motor home, or private motor coach as defined in s. 320.01 may be more than 102 inches if:

(a) The excess width is attributable to appurtenances that do not extend beyond the exterior rearview mirrors installed on the motor home by the manufacturer or the exterior rearview mirrors of the tow vehicle; and

(b) The exterior rearview mirrors only extend the distance necessary to provide the appropriate field of view for the vehicle before the appurtenances are attached."

Also many trailerable boats have a wider beam. An Overdimensional Roaduse Permit is easy to obtain. Not all over-width special permits require escort vehicles. These permits are available as trip permits or blanket permits.

I would think other states would have something similar, and interstate permits are also available.

Road Fan

I hadn't meant to imply there aren't provisions for wide vehicles, we see them in Michigan all the time.

genec

Exactly... and the irony is that on California high speed arterial roads, speeds may be as high as 65MPH (by speed limit) and yet the same narrow 4 foot bike lanes typically exist, if there are bike lanes. Interstate freeways on the other hand typically have shoulders that can be 8-10 feet wide, while again the roadway is signed at the same 65MPH.

genec

No problem... just pointing out that a "shareable lane" may not be all that shareable under certain conditions.

Your other data is quite good and appreciated.

wahoonc

I live in the depths of North Carolina...bicycles are considered a nuisance vehicle.

I was curious as to road width where I ride on a regular basis. So I put on my nice ANSI Class 2 Safety Vest and grabbed my measuring wheel. None of them have enough lane width IMHO for sharing. The main road in front of my property 22' from fog line to fog line, allowing 1' width for the center stripe. There is occasionally up to 20" of pavement to the right of the fog line, in some places there is none. The speed limit is 55mph and services over 6,000 vehicles per day on average. That volume will be increasing as they continue to build subdivisions further out.

The next road over (the one I have to take to get anywhere is barely 18' from fog line to fog line and has a double yellow line that is 12" wide the edges of the road are broken down in many places reducing the lane width by 18" or more. These roads are 55 mph posted and have traffic volumes in the 3,000-4,000 vehicles per day range. The area is hilly, curvy and quite often you have limited sight distances. The main four lane into town is built to a better standard. It has 12' lanes with 6' shoulders and is a divided four lane. The posted speed limit is 55mph but average is probably 65mph+. Traffic volume is over 25,000 cars per day. For the most part I feel safe riding it, however I really wonder when I see banged up guard rails on the long straight sections...

As far as gauging the width, I figure a standard full sized pickup is around 7' wide a full sized semi 8' small sedans I give 5.5'. Regardless I am not a fan of lane sharing until they can stop drivers from all the distractions they currently have; cellphones, eating, video players on the dash, etc, etc. Driver training in the US needs to be drastically improved.

Aaron

LS2379

Most roadways are now designed with 12' lanes. Some older roads can be 11'.

bikesafer

I think it was me who you are talking about from the thread yesterday. I just wanted to clarify something, the numbers I was adding up were conservative numbers, numbers that bike un-friendly people would/have quoted to me.

Most bikes I own are about 2 feet wide, most bike safety publications I've read say to allow yourself 3 feet of clearance from any obstacle, and I would consider a gravel shoulder or gutter pan to be an obstacle, so that's 5 feet plus the 3 feet of clearance from the passing motorist and that adds up to 8 feet plus the width of the car. Most of the lanes I ride in range from 9 feet to 12 feet with some as low as 8 feet. I can guess pretty well because I too have taken a tape measure to many of them. The other variable is size of the passing car. Most passenger cars are at least 7 feet wide. Most cops will tell you that they are not that wide, but the width measurements given by many manufacuturers don't include the mirrors, which any cyclist can tell you is what is most likely to hit you. If there is a large SUV or truck then there is rarely a lane I ride in that would be share-able with that size of vehicle.

As far as where the lane ends, according to the Manual on Uniform Traffic Control Devices, the white edge line is the edge of the roadway, so anything beyond that is shoulder, at least in places that have adopted the federal Manual on Uniform Traffic Control Devices.
In Wisconsin cyclists are not required to ride on the shoulder, but if there is a wide (4 or 5 feet) clear shoulder and a 12 foot lane, you might have a hard time explaining to the judge how it is reasonable to take the lane when there is a 5 foot shoulder available. When I run into this scenario I ride the shoulder, but this is rarely the case. I'm not a lawyer and I don't play one on TV your mileage my vary.
Bikesafer
Jeff

genec

In my area there is a relatively new freeway paralleled by a very nice class 1 bike path. From the travel lanes of the freeway to the bike path there is the road shoulder... about 8 feet wide, then a landscape area, perhaps 10 feet wide... even wider in some areas, then a sturdy 6 foot high chainlink fence. The chainlink fence has been breached in several locations... obviously from the freeway side as the fence is pushed in toward the bike path; in one spot it is obvious that a motorist drove through the fence from the freeway and then drove back out the fence a short distance later. The freeway is NOT a winding mountain road... it has good sight lines and gentle curves as it runs east-west. I know a certain cycling advocate that likes to "blame bike lanes" for the deaths of cyclists when such collisions occur... To me the evidence of the damaged bikepath chainlink fence 18 feet or more from the freeway lanes tells me that it is motorists, not paying attention or distracted, or drunk, that are the problem... not lines in the pavement, nor fences along the freeway.

It is a bit disheartening to see this damage in the fence and realize that if not for the fence, perhaps a cyclist would have been harmed.

It really does make me wonder about "sharing the road" at all.

Da Tinker

ASHTO standard for lanes is 12'. As a point of comparison, Texas law specifically allows cyclists to take the full lane when lane width is less than 14'.

My default position on the road is about arm's length from the right ridable edge, or about 2 - 3 feet. How much clearance I want from passing vehicles is a matter of relative speed. More differential speed = more clearance desired. I'll share a 12' lane with a car that has a 10 mph speed advantage. Don't care to share 16' lane with a dump truck with a 50 mph advantage.

wahoonc

My point exactly. American drivers are some of the least trained people in the world. I have long advocated better driver training and responsibility. The current 40 or so hours of training and no required additional training is obscene. We spend billions upon billions of dollars to make roadways safer, cars safer but very little to make drivers safer.

Sharing the road is fine in some situations, but in most I think separate facilities would be much better. Also how are you going to get beginning cyclists like younger children out riding if you have to share roads with incompetent motorists? The Dutch and many others got it right, unfortunately we haven't.

I was reading the statistics for bike crashes in NC involving cars. Interesting reading...most accidents occur during daylight on the slower urban streets.

Aaron

Roody

Narrow lanes rule!

The narrowness slows down the drivers, and forces them to merge fully into the next lane to overtake me. Even if I ride in the center of a very narrow lane (or the left edge at night), the drivers can see that I'm only taking my fair share, so they don't get mad.

I greatly prefer narrow lanes to standard lanes. Of course, VERY wide lanes (>14 feet) are even nicer, but they're pretty rare.

I-Like-To-Bike

It would have been more interesting if the report gave ANY indication of exposure, i.e what percentage of bike riding is done during daylight on slower urban streets vice the alternative less favorable conditions.

From the same report: "In other words, the crashes are related to exposure. The crash fact descriptions that follow are also undoubtedly related to exposure, or when and where people choose to ride."

Unfortunately, the report gives zero information about that exposure.