“Shoehorn” Bike Lanes

Attention bicyclist advocates: resist the urge to desire dedicated bicycling facilities when they won’t fit safely.

In the accurately scaled example diagram below (visit iamtraffic.org to tweak the dimensions and vehicle choices. A very cool tool!) a cyclist riding an upright bike is riding centered in a 5′ BL w/curb abreast of a Ford F-150 driving centered in the right general purpose travel lane (and DON’T say “car lane”, or somesuch).

illustration from iamtraffic.org interactive tool
illustration from iamtraffic.org interactive tool

Notes on the illustration

These dimension are generally viewed as be minimally acceptable for safety in areas with curb, see e.g. AASHTO Guide for the Development of Bicycle Facilities

The recommended width of a bike lane is 1.5m(5 feet) from the face of a curb or guardrail to the bike lane stripe. (2012, p. 4-14. Then goes on the state reasons when BL should be wider)

Along sections of roadway with curb and gutter, a usable width of 4 ft (1.2 m) measured from the longitudinal joint to the center of the bike lane line is recommended (2012 p. 4-15)

Note in the illustration is slightly below the 4′ of usable width recommendation; because typical city gutters are something a little more than 1′ wide (as mentioned below, 1.5′ pans are typical for the Phoenix metro area). And note this is all presuming there are no drainage grates (or anything) protruding beyond the gutter pan). Any such hazards would necessitate the overall BL be more than the 5′ shown.

The more insidious problem is that of the dimensions of the travel lane. An 11′ travel lane is considered generous by city standards, yet we see that many vehicles being driven centered in that lane will not pass at the legally required 3′ of clearance. Many vehicles would need to be driven consciously to the left of their lane in order to pass at the minimum of 3′. And by many I mean many — the Ford F-series pickups are the most popular vehicle models in the US, and have been so for decades. Larger vehicles, medium and heavy-duty trucks and buses simply cannot pass legally without changing lanes — will they?

from Figure 3-1 Bicyclist Operating Space (widths), AASHTO Guide ... 2012.
from Figure 3-1 Bicyclist Operating Space (widths), AASHTO Guide … 2012.

Cyclist’s minimum operating space

The iamtraffic illustration above accurately depicts what the AASHTO Guide calls  the physical width of (an adult on a single-track, upright bicycle) cyclist of 2.5 feet and a minimum operating width of 4 feet . The operating width is depicted by a pale yellow highlight which is there but difficult to see because there is so much encroachment at the illustrated width (a 5′ BL, next to a 11′ travel lane).

The FHWA Bicycle Road Safety Audit offers these guidelines and explanations:

On-road accommodations: bicycle accommodations should consider the full operating width of cyclists, not just the physical width. The operating width for cyclists may increase because of speed, wind, bicyclist’s handling skills or shy distance from curbs, gutter pans, drop-offs, guard rails, railing, car door swing, and other features.

On-road accommodations: …Bike lanes or separated facilities may be more appropriate on high-speed, high-volume roads. Adequacy of the separation distance of these facilities is a function of vehicle speed, volume, and composition. Beyond meeting minimum standards, the width of on-road facilities should consider the wind impacts from passing heavy vehicles.

Designated BL in City of Tempe
Designated BL in City of Tempe

In the diagram, the cyclist, and her minimum operating space, is shown centered in the 5′ bike lane — this is not necessarily realistic due to the inevitability of inconsistent gutter pan joints, especially when exacerbated poor maintenance (like the photo at right), along with debris that naturally collects at any road’s edge and no amount of sweeping can eliminate (example of another maintenance problems ,  example of sweeping).

Baseline Road

There is a section of Baseline Road, between about 40th to 46th Street (why not 48th St / the city limit? East of 48th is City of Tempe, by the way) which lacks BLs. The City of Phoenix installed BLs west of 40th Street (to ??) some years ago.

The nature of this street is it is a high speed / high volume (with significant heavy truck traffic), posted 45mph limit primary arterial with 3 through lanes in each direction. It sometimes becomes congested, I guess especially eastbound due to I-10 interchange just east of City of Phoenix. In this section the east and west lanes are separated with a raised median.

The dimensions are apparently 35′ curbface to curbface (for each direction, separated by a 20′ raised median); divided something like 12 / 11 / 12 which includes a gutter pan (see CoP email from 2006, below). Here is a streetmix of one proposal for squeezing a BL in there (that one assumes the gutter somehow gets incorporated into the BL, either by paving over it, or digging/cutting it away).

There is no honest / ethical way to rearrange 35′ of space and maintain three through general purpose travel lanes and a BL. As we’ve seen above, a minimally acceptable BL plus one travel lane takes up 16′, and it is unlikely the city would ever install two travel lane (one next to a curb) in 19′ of space.

Moreover because of the high speeds plus expected heavy truck/bus traffic, a wider than 5′ BL is indicated.

There are only two ways to add BLs to this strech —

  • Reduce the number of through travel lanes in each direction from 3 to 2, or
  • widen the road

Besides AASHTO, there are other “guides”, e.g. the NACTO Urban Bikeway Design Guide: says on the topic of BLs:

On streets with high traffic volume, regular truck traffic, high parking turnover, or speed limit > 35 mph, consider treatments that provide greater separation between bicycles and motor traffic such as: Left-side bike lanes (not applicable in this configuration),  Buffered bike lanes, or Cycle tracks

City of Phoenix, by the way, is some sort of founding member of NACTO. So 3 of those 4 items apply to Baseline Rd, so a Cycle track, or Buffered BL should be used to provide “greater separation” — either of which would require far more space than a 5′ BL.

14footLaneHere are some more graphics; this one shows lane sharing in 14′. The bicyclist’s tire is 2′ from the edge; i.e. a FRAP, and the pickup is literally as far left as possible — there is less than 3′ clearance. You can regenerate other graphics (e.g. with a car, which shows enough clearance, or a Truck which show the two practically touching). I will check with iamtraffic, i am quite sure you/we can use their graphics so long as we credit them.

Truck/Bus Dimensions

Figure 8.3. Recommended lane widths for curbed roads

Some diagrams in The Influence Of Lane Width On Bus Safety may be useful. In Figure 8.3. D is 8.5′, E is 1′.  Recommended lane widths for curbed roads, they came up with 12′ lane (dimension J in the figure) next to G=5′ BL, THAT’S SEVENTEEN FEET (including a 1.25′ gutter, marked as A) as a recommended width — presumably a recommended minimum width because they fudged in ignoring the right mirror dimension, in other words, the width of the mirror is ignored for the purposes of a 3′ minimum passing clearance. There is also a second fudge in that the operating space depicted (B= 3.75′) is less than AASHTO recommendation of 4′. A third potential fudge is underestimating the width of the gutter pan (A = 1.25′), around here they seem to be more like 1.5′. So sort of a worst-case fudging is an extra 13 to 18″ (10 to 12 inches for the right-mirror, and 3 to 6 inches for the bicyclist’s operating space) is really required to provide a minimum clearance of 3’… Which is not to say the 3′ can be assumed or guaranteed to be safe. The law, quoting AZ law is that passing drivers must allow a “…safe distance between the motor vehicle and the bicycle of not less than three feet”. What this all adds up to is one quite wide lane; if you’re planning or hoping to have legal and safe passing in-lane next to a BL.

mirror strike warning sign; somewhere in WA state.

Other illustrations may be helpful, E.g. “Figure 2.10. Buses not able to maintain a 3-foot clearance law from the bicycle for a 14-foot wide curb lane”.

Baseline Road is a truck route (see this article for explanation of truck routes in the City of Phoenix); and is not only an arterial, but a principal arterial, and this stretch is located adjacent to the confluence of two major freeways: the I-10 and US-60. Expect lots of truck and bus traffic.

Apache Trail 3 to 3+BL re-striping

This is just a coincidence, but I noticed that according to google street view BLs appeared on Apache Trail in the vicintiy of Ocotillo, Apache Junction sometime after June 2013 but before July 2015.

The road was used to be 3 lanes in each direction plus left turn pockets with a (very wide, and not raised) median — but was according to google estimates 38′ wide. So they did something like 11/11/11/5′ (including gutter)… which quite minimal as shown above (and check out the PU in that particular street view).  An 11/10/12/5′ split would be much better. And since there’s no curb at the median, if you really wanted to do usable segregated bike facility: 10/10/12.5/5.5 (i.e. a minimal BL — 4′ of usable space plus 1.5′ gutter pan) would be good — trucks and buses could pass within lane and still give cyclists in the BL the required passing clearance.

Sidenote: the BL symbol appears to be non-standard; the standard symbol is 40″ wide; this one looks to be only maybe 24″???

Broadway Lane Diet

Info on the Broadway Road lane diet has been moved here; the geometry is arguably shoehorn, 11′ travel lanes next to a “5 foot” BL. I put that in quotes because that’s shorthand for saying it’s a 3.5′ BL next to a curb/gutter. (it’s even as little as 3′ in some places).

Advice on Shoehorning from the FHWA

Released advice on how to shoehorn in bike lanes in Incorporating
On-Road Bicycle Networks into Resurfacing Projects.  [.pdf version] Things like this, of course, sound very reasonable, p.2:

…transportation agencies are encouraged not just to meet the minimum requirements of providing bicycle facilities, but to go beyond minimum standards…

For travel lanes, the smallest allowable width; which they say would tend to be 10 or 11′ (p.23). For BL’s I don’t think they say(?) — I would presume they mean “5 foot” BLs — which tends to mean 3.5′ of usable space next to a 1.5′ gutter/curbface. (which is actually less than the 4′ usable space recommended in the AASHTO Guide… as the minimum operating space for a design-bicycle/bicyclist, see figure, above from the Guide). They also refer to a “standard width” BL; so anyway, i haven’t found where they say what they exactly mean by standard and minimum width BLs.

There are several, very weak, cautions and warnings, mostly collected on p.33:

3.4 | Practices to Avoid
There are several practices that should be avoided when resurfacing streets and roads. Some of these can actually make conditions worse for bicycling than simply returning the roadway to the same lane configuration as before resurfacing. In many cases, minor modifications to project plans can mitigate problems for bicyclists.

Overuse of Design Minimums
Methods discussed in this workbook call for flexibility in the use of design criteria, particularly travel lane widths. Without reducing travel lanes to a minimum width, it will be difficult to use that particular method effectively. It is not necessary to use minimum widths for an entire street cross-section. If a travel lane is proposed with a minimum width, the adjacent bike lane should be standard width. If minimum widths are used in combination (i.e. minimum width travel lanes and bike lanes), consider the following…

Some Details about Gutter Pans

Gutter pans can vary, or not even exist at all. Typically local agencies in MAG uses a 1.5 foot [it’s actually 17″; which is 24 minus 7 on the MAG drawing referenced below] gutter pan next to a vertical curb. (by comparison ADOT typically uses 24 inches). See Vertical Curb and Gutter (Type A), detail 220-1 in the MAG document Uniform Standard Details for Public Works Construction. Each local agency also has their own details that are referred to as Supplement to the MAG.

There are some oddities I’ve only ever seen in Tempe, see e.g. the Broadway Road lane diet project; they use 17″ usual gutters everywhere except it flares to 24″ near each intersection, this squeezes an already shoehorned bike lane even more.

It’s also possible to use a very wide pan as a bike lane.

Some other actual measurements

I’ve begun to note actual widths at places of interest. A 700C-25 wheel is 2015mm = 6.906 feet. It’s pretty easy to measure revolutions, so for example 5 revolutions = 34.5′ — a common width for curb-to-curb for 3 through lanes in the City of Phoenix where there are raised medians.

Ray Road near Sun Ray park = just shy of 5 revs = 34 feet. In its present configuration, it’s ~ 11 / 9.5 / 9.5 / 2.5 / 1.5 (lane 1 / lane 2 / lane 3 / asphalt shoulder / gutter; and is very much a #fakebikelane). 34 feet is a very unfortunate choice of dimension. A minimal BL would be 4′ plus 1.5 gutter, leaving 3 lanes in 28.5 feet (= 9.5 feet). Something the city would likely never do because, you see, it’s important for safety that general purpose travel lanes be wide enough, but bike lanes or fake bike lanes do not need to be. Note that as with many raised medians there is “extra” space in the median — I mean it is wider than one lane. The median here appears to be about 15 feet.


9 thoughts on ““Shoehorn” Bike Lanes”

  1. From: mike cynecki @phoenix.gov
    Sent: Wednesday, November 01, 2006 12:24 PM
    To: Michael Sanders
    Cc: jenny grote @phoenix.gov
    Subject: RE: Baseline east of 40th St to 46th St

    Michael – I learned that each direction of Baseline is 35 ft from curb face to median curb face. That does not give us much room to work with.

    To get the most that we can, we are restriping with a 12’/10’/13′ so that the outer lane along the curb is at least 13 ft wide. We need to maintain a 12 ft curb lane next to the median, and 10 ft is the narrowest that we can go with for the interior lane.

    We are at the mercy of the original designers of this street. Now all of our arterial streets have on-street bike lanes as a part of the normal cross-sections. This segment was built too long ago.

    Mike Cynecki
    Traffic Engineering Supervisor
    Street Transp. Dept.

    Lanes which are wider than normal, but not wide enough to share side-by-side, such as the 13′ lane (minus gutter, so ~ 12′) referred to above by a presumably well-meaning but misguided individual are DISASTROUS for bicyclists, the “sharing” of the lane turns out looking like this illustration, if the bicyclist is lucky, lots of very close passes:

    Too narrow to share...

  2. If the city is unwilling to make room for bike lanes, then the only other way to safely accommodate bike traffic on the road is to mark the right lane with a sharrows, add BMUFL signs, and reduce the speed limit to 30 mph or less, preferably with some traffic calming measures to encourage drivers to slow down.

  3. From Article by Wayne Pein 2012 AASHTO Bike Lane Width

    Where a concrete gutter pan has been covered with asphalt, the bicycle
    lane is measured from the virtual hidden edge of the gutter pan. A longitudinal crack will develop along the gutter pan edge due to differing expansion and contraction rates and loading…
    …The gutter pan, whether visible or covered by asphalt, is not usable space and is not inclusive in bicycle lane width as was clearly stated on page 23of the 1999 AASHTO Guide for the Development of Bicycle Facilities:
    “The width of the gutter pan should not be included in the measurement of the ridable (sic) or usable surface…”
    Moreover, in discussing shared lanes on major roadways of the 2012 Guide it says on page 4-3,
    “The gutter should not be included in the measurement as usable width,…”

    Image 1. Clearly visible longitudinal crack in the asphalt covering a concrete 2-foot wide debris-filled gutter pan. MLK Jr. Blvd., Chapel Hill, NC.

    I don’t know where that pic was taken, but here you can see from the various dated street views, 2012 seem to be the worst condition, the deterioration of the asphalt surface covering of the concrete gutter pan

    Also extracted from the same article/paper, Pein’s critique of AASHTO BL widths,

    2. When operating at lane centers, a 12-foot travel lane and 5-foot bike lane (17 feet total) offer just 3 feet of clearance between bus body and bicyclist. A motor vehicle skimming the bike lane line results in 1.25 feet of clearance.

    There are also many pearls of wisdom in another of Pein’s whitepapers, How wide should a wide lane be?

    Further, a standard 12-foot lane plus a standard BL of 4 feet totals 16 feet. Additional width should be added to the BL when the standard lane is narrower than 12 feet. The North Carolina Bicycle Facilities Planning and Design Guidelines states, “Additional width also is desirable when the width of the adjacent traffic lane is less tan 3.6 m (12 ft). This is an important addition because the effective clearance between a bicyclist and adjacent traffic is a function of the combined width of both the bike lane and the adjacent traffic lane.” In essence, the total
    pavement width when BLs are present should be 16 feet or more.

  4. Road users need to impress upon the City traffic engineers that this “needs to be killed”:

    A popular trend in recent years has been to divide a roadway with 24ft of width in each direction into what’s known as a 10-10-4. This is done to shoehorn minimal (4ft) bike lanes next to narrow (10ft) travel lanes. This helps no one. It scares the crap out of novices and takes away the right of informed bicyclists to ride in a safe and defensive manner. The trend needs to be killed. – See more at: http://commuteorlando.com/wordpress/advocacy/widths-buffers/#sthash.FfcG9ALs.dpuf

    Many state engineering guidelines use 14ft as a lane width that accommodates same-lane passing of bicyclists. On a road with trucks, buses, utility trailers or any other large, commercial vehicles, 14ft is NOT wide enough to share. It is not safe, therefor it is not PRACTICABLE. – See more at: http://commuteorlando.com/wordpress/advocacy/widths-buffers/#sthash.FfcG9ALs.dpuf

    Other voices: https://gettingaroundsac.wordpress.com/2015/02/04/14-foot-lanes/

  5. ADOT Roadway Design Guidelines 2012 Edition (which appears to be current with the most recent, 2014, updates and revisions —
    Page 300-11, section 302.4 — Shoulder Width, Table 302.4: Urban multi-lane divided or undivided 5 or more lanes, (what about Urban undivided 2-lane?), or Frontage Roads (2-lane) One or Two way: The right shoulder width for all of these is 4 feet
    And note 2 states “For shoulders with curb and gutter, widths include gutter pan”. (ADOT gutter pans are two feet wide, by the way).

    Page 300-48 Urban Highway Typical Sections, Figure 306.4A
    Contains diagrams for 3 typical sections, UA UB and UC:
    Sections UA and UB (curb-and-gutter) has a 16′ from lane line to curbface, along with the notation:
    Consider 17 ft. on a project by project basis to accommodate bicyclists. Consider factors such as location , vehicular traffic, grades, anticipated bicycle usage and right of way availability.
    Section UC (no curb-and-gutter) is shown with a 12′ right lane, then 4′ of something (presumably shoulder, presumably with an edge line?), then 8′ of sloped away space.

    So here’s where we get these ADOT fake bike lanes, on e.g. Price Frontage road: a 12′ right lane with an edge line enclosing a 4′ shoulder which includes a two-foot wide gutter pan.

  6. apparent shoehorn geometry; City of Phoenix
    Washington St along the light rail.
    jefferson St along the light rail

    These examples, the van and pickup, are about 8′ wide including mirrors. Appears to be a full-sized van, and something like a ford f-250 pickup.
    Transit buses and trucks can be about 10′ wide including mirrors.
    These are low-speed (25mph posted, i think), low-volume frontage-style roads.

  7. SR89A at Pinon Dr; west Sedona.
    I see from street view history it was done sometime after 2011 and before Oct 2016. https://goo.gl/maps/NwjF4B56mgr

    So let’s see; we’ve got a designated BL with 2′ of usable space next to what looks like 11′ travel Lane. Is that right?

    Why would ADOT allow this? (or doesn’t adot “own” this segment?).

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