About the Austin Bicycles May Use Full Lane report

This is a review of an Austin, Texas Bicycles May Use Full Lane (BMUFL) sign report.

All in all, I consider this a useful report, though it has serious weaknesses. The finding that the BMUFL sign improved motorist behavior is encouraging, though the improvement was not as great as to be hoped.

That many bicyclists did not take advantage of the signage is to be expected, for three reasons which I can discern:

• many are fearful of riding on roads with narrow lanes in any case;
• there was no educational campaign; and also,
• the signs are primarily directed at motorists.

It is not surprising that the shared-lane marking study conducted at the same time as this study (and which I also have reviewed) showed more success in changing cyclists’ behavior, because shared-lane markings are directed at bicyclists.

I would venture that wide acceptance of cycling on narrow urban roadways requires education; also, particularly for child cyclists, diversion of through motor traffic to other roadways using a “bicycle boulevard” approach like that in Berkeley, California. I would be most interested to see this tested in Austin, which, like Berkeley, has a street grid amenable to such treatment.

In the executive summary, I note the following:

Additionally, safe motorist behavior was defined by two factors: (1) motorists gave adequate space to bicyclists when passing and (2) motorists did not encroach on adjacent lanes when passing.

I can’t make sense of this. That is to say, it is hopelessly confused. The lanes in this study are 11 feet wide, too narrow for a bicyclist and motorist to share safely side by side. If a lane is too narrow to share, then motorists can only overtake safely by merging their vehicles partly or completely into the next lane. Where it is legal to merge into the next lane, as on both streets where the experiment was conducted (four-lane two-way streets), then merging is not “encroaching.”

In the section on Experimental Design, I note that the lateral position of bicyclists was measured at their wheel track, and that of motorists, at the right side of the vehicle’s right-side wheels — see Figure 9 in the report. This measurement is meaningless. Bicyclists’ handlebars extend as much as 12 inches either side of the wheel track, and motorists’ rear-view mirrors may extend several inches to the right of the wheels, and more for large trucks and buses.

In the list of definitions, the term “avoidance maneuver” is used incorrectly, as it is in the bike box report, which I also have reviewed:

Avoidance maneuver An avoidance maneuver was recorded whenever a bicyclist rode outside of the lane (e.g. rode on the sidewalk or cut through a driveway to turn).

This is a choice of route, not an avoidance maneuver, which is an emergency maneuver to avoid a collision.

There are other confused definitions:

Incomplete passing event – An incomplete passing event was recorded when the motorist passed a bicyclist without changing lanes.

This is an in-lane pass, not an incomplete pass. An incomplete pass would occur if a motorist initiates a pass and then decides not to pass.

Encroachment – Encroachment was recorded when a passing motorist occupied two lanes while passing.

This is not encroachment, as already mentioned. It is a straddle pass, as defined and named accurately by Dan Gutierrez and Brian DeSousa, see citation below.

In the section on Results —

The bicyclists’ change in lane position is statistically significant due to the large number of data points. In spite of what the report says, it is operationally insignificant, amounting to only three or four inches. The change in clearance between motor vehicles and bicyclists due to motorists’ different position, on the other hand, is significant both statistically and operationally. (But do remember, the bicyclists’ position is measured at the wheel track, and the motorists’, at the right side of the right-side wheels. Actual clearances are smaller than those described in the report by about 1 1/2 feet. That makes the differences more significant operationally.)

Accounting for this, motorist lateral clearances from the curb and from bicyclists during passing events (Figures 12 and 13) are scary indeed. Clearances following installation of the signs are not as tight, though they also could be greater. Bicyclists’ not claiming the lane invites the close passes.

Quoting:

Regarding motorist behavior, it is interesting to note that the ratio of passing events to non-passing events decreased significantly, while the proportion of passing motorists who encroached while passing increased. These results lend themselves to the hypothesis that as bicyclists took a stronger position in the lane, the motorists who did choose to pass found themselves taking a stronger position in the lane that caused them to encroach on the adjacent lane.

In spite of the incorrect terminology, this result confirms the result of Gutierrez and DeSousa’s research (see citation below)..

And quoting again:

Regarding bicyclist behavior, the implementation of the “Bicycles May Use Full Lane” signs did not discourage sidewalk riding. It is uncertain whether the bicyclists who avoid the motor vehicle lane are regular commuters and recreational bicyclists who prefer to ride outside of the motor vehicle lane or if they are simply neighborhood children or inexperienced bicyclists. Regardless of their experience level, it appears that the addition of signs did not significantly change the proportion of bicyclists who use the motor vehicle lane.

The data analysis could not identify different categories of adult cyclists but I don’t see why it couldn’t identify children. The researchers use more incorrect terminology, extremely obtuse at that. How is a lane with signs indicating “Bicycle may use full lane” a “motor vehicle lane”?

The finding that cycling on sidewalks increased greatly after installation of the signs on Cesar Chavez boulevard begs for an explanation. I don’t see how installation of the signs would affect this one way or another.

In the section Conclusions and Recommendations:

I quote:

It should be noted that encroachment is only dangerous when there are vehicles present in the adjacent lane, and this study did not note whether or not this was the case.

What is being described is normal changing lanes to overtake a slower vehicle. It is being described as dangerous and as encroachment. This is bizarre.

In the section on References:

None of the references is to another study of the BMUFL sign, as this is the first one. However, Gutierrez and DeSousa’s study of overtaking clearance deserves attention as a study of the effect of bicyclist lateral position. These researchers also developed the accurate and values-neutral terminology, in-lane pass, straddle pass, lane-change pass, which compares very favorably with the confused terminology of the Austin report..