I wrote this article several years ago but feel bumpouts are still a relevant and under analyzed area of traffic engineering. I still receive question from readers and clients about crosswalk bumpouts and their effectiveness and felt it was timely to share this article again. Have you seen an improvement in pedestrian safety through the use of crosswalk bumpouts? Send us a message – we’d love to hear from you.
Mayor Stu Rasmussen of Silverton, Oregon sent me the following email questioning the effectiveness of bumpouts (aka bulbouts or curb extensions):
I am wondering about what looks like a current fad in traffic engineering and was hoping you might have some empirical data to back up the current practice. Bulbouts or curb extensions are the current rage for crosswalk safety modifications. They are supposed to shorten the crossing distance and improve visibility of drivers and pedestrians for each other.
Definitely, the distance crossing active traffic lanes is reduced. To me that means that at a signalized intersection the cycle time can be accelerated because shorter distance for pedestrians means faster transit time.
At an uncontrolled intersection the benefits are not so clear to me. If a pedestrian approaches the active traffic lane on a bumpout, does a driver really know they’re going to immediately cross the street or could the pedestrian just get to the extended curb, stop, re-think their route, daydream for a while and then reverse course and wander off. All this time, the driver, if he/she is properly attentive, will be stopped while waiting for the ped to cross. After a few of these driver/pedestrian encounters it seems to me that drivers may become desensitized to the pedestrian – since it is entirely possible that no street crossing will occur.
Conversely, without a bulbout a pedestrian is obviously going to cross a street if he/she has actively stepped off the (non-extended) curb and entered the parking zone of the street. There is no question in a drivers’ mind of the walker’s intent, and the pedestrian is clearly visible at the edge of the active traffic lane as he/she approaches.
I am wondering if there is any unbiased empirical data supporting the addition of bumpouts to crosswalks – before and after studies of accident rates with and without the bumpouts – that would shed some light on this practice.
This gave me pause because I recommended bumpouts for an issue in Pine Island, MN (read about it here). They’re highly touted in pedestrian planning documents.
I spent some time digging and couldn’t find any research online about the effectiveness of bumpouts. I did find a mention in NCHRP Report 617 on crash mitigation measures that stated no research was available on the topic. So I posed the question to the ITE Traffic Engineers Listserv I’m on.
Dwight Kingsbury of the Florida DOT came back with this study from Oregon. The dataset shows positive results, but the sample size isn’t very big. I think I’ll stand on the side of bumpouts enhancing pedestrian safety, but more research would be nice to quantify the benefits.
I’ve driven through Pine Island many times, as it’s generally the way I travel from the Twin Cities to go visit my parents in Byron. The original post-reconstruction, pre-bumpout design in Pine Island was horrible for both drivers and pedestrians, and I really appreciated the planters when they were put in. The arrangement seems a bit ungainly, but it definitely does the job of calming traffic and giving pedestrians a more comfortable refuge.
The traffic lanes wander side-to-side on both the north and south approaches, so I never even knew where to drive before the planters arrived. I remember stopping in downtown Pine Island on one trip and making use of the angled parking on the southbound side — it was easy to get in and out, but I couldn’t even find the traffic lane again when I departed. I ended up somewhere in the (now absent) right-turn lane. Curving pavement, poor contrast between white/yellow paint and concrete, and just an incredibly wide street (82 feet curb-to-curb!) all contributed to create a messy situation.
The old configuration before reconstruction (which wasn’t all that great but didn’t feel especially bad either) had two sets of 4-way stop signs on Main Street. That was reduced to just one 4-way stop afterward. After the bumpouts were installed, car drivers were being more courteous at both intersections than they’d ever been.
Of course if it wasn’t obvious already, the bumpouts in Pine Island are massive (at least on the southbound side) — the planters are impossible to miss. Most streets will have lower-profile curb extensions instead, though I still feel they can be very effective.
I don’t really agree that “a pedestrian is _obviously_ going to cross” if they move into the parking lane. They might just be trying to get better visibility to determine if crossing is safe or not. I also personally feel that drivers are _less_ likely to notice pedestrians timidly stepping out into the street than they are to see them standing much more confidently on a bumpout or other refuge.
But, that’s just my feel for things. Certainly more actual data would be appreciated.
I see four advantages:
1- easy access for the handicapped.
2- better visibility in case of parked vans or trucks.
3- encouraging pedestrians to cross at one point instead of dispersing along the street, trying to find a gap between parked cars.
4- traffic calming, plausible view, and more pedestrian friendly.
I guess I will propose few bumpouts to our local municipality and will collect data before and after.
I don’t really see the difference from the driver’s perspective. The curb is now moved, either ped steps in the crosswalk or does not step in. If steps in, driver yields. If not, ped has yielded. If ped is walking purposefully toward the intersection without deceleration, the driver should assume the ped has asserted ROW. Anyway, no distinction except the pedestrian is now *more* visible.
Very good blog article.Thanks Again. Fantastic.
In the documentation i have in my possession i do not find evidences of concerns in the problem you presente: “After a few of these driver/pedestrian encounters it seems to me that drivers may become desensitized to the pedestrian – since it is entirely possible that no street crossing will occur.”. Although it do not mean this problem do not exists.
I have a little reference to a Danish study where it is stated that the reduction of the cross distance through the implantation of bumpouts reduces the number of accidents due to crosswalk use by 57% to 82%.
This studies results, in my opinion, cannot be applyed to diferent cultures or even to different situations.
It is also stated that the reduction of lane wide increases the atention of the driver.
WHat i can think of to, somehow, try keep drivers sensitized to the crosswalk is to inflect them a fisical warning to the crosswalk such as diferent pavement texture ( increasing sound and vibration in this zones), a bump crosswalk (upland crosswalk) to obligate the driver to reduce its velocity
The scenario of the daydreaming pedestrian could happen anywhere, regardless of the curb type.
I’ve not experienced a problem with excessive yielding, but there is plenty of evidence of drivers not yielding enough to pedestrians.
In addition to the shorter crossing distance, the bump out puts the pedestrian in a position to be more visible to drivers. The narrowing of the traveled way has a calming effect on drivers, and lower speeds improve safety to the pedestrian.
I will keep recommending bump outs (where appropriate) knowing that shorter travel distance, improved visibility, and lower vehicle speeds are all empirically safer for the pedestrian, as long as there is no evidence that bump outs themselves present a hazard.
The phrasing of the question suggests to me a fear of the unknown, which is quite common for non-engineers when faced with new and unfamiliar infrastructure solutions. Perhaps the mayor has a test site in mind, and can conduct a local study?
More research is a great idea! the LRRB is looking for research topics…. Here is the link to the page: https://lrrb.org/contact-us/submit-ideas/
Hengel, D. Build It and They Will Yield: Effects of median and curb extension installations on
motorist yield compliance. Presented at the 92nd Annual Meeting of the Transportation Research
Board, Washington, D.C., 2013
One negative is that unless they are designed with protected bike lanes in mind, they usually preclude or make it really difficult to convert a corridor into some form of protected bike lanes.
They’ve been putting curb extensions everywhere in my county for the past 20+ years. Now with the recent push for protected bike lanes, the County is going to have to spend millions modifying the curb extensions in order to install protected bike lanes.
I prefer using a median refuge island at a mid block pedestrian crossing for the following reasons:
1. The pedestrian crossing distances are shortened.
2. The number of available gaps is substantially increased due to the two stage crossing.
3. Vehicular traffic is deflected and forced to slow.
4.They are far easier for snow plows to negotiate if the island is properly shaped like a trapezoid. (Think about the plow blade angle versus the curb line on a bulb out.)
5. Bulb outs may cause less parking to be lost, but the driver’s view of pedestrians trying to cross is not likely to be occluded with a median island design as it could be by parked larger vehicles near a bulb out.
6. If the street has a TWLTL they are easy to add.
The recommended island width is 10 feet.
If taking the Mayor’s logic, if pedestrians push the button at signalised intersections then wander off, does it mean drivers would see it as waste of time and run the red light regardless?
Kerb extension is a tool help all road users to be visible to each other and its application would have been proven necessary at the first place. No device could be ensured to meet 100% of its desire intention but the benefits to me is very clear and obviously outweigh the so-called frustrations.
The link to the Oregon study brought up a “404 Error”
Thank you for notifying us about the break in the link. The link has been updated.
i like how mayor Rasmussen bases his doubts about bumpouts on rhetorical questions (“does a driver really know?”), baseless speculation (” drivers may become desensitized…”), and unsubstantiated assumptions (“there is no question in a drivers’ mind…”), and then asks you to provide unbiased empirical data in support of them.
I understand these newest bump installations are meant to help the visually impaired. Why oh why however are these “improvements” not more thoroughly thought through from all angles. It has now become much harder for wheelchairs, manual and electric to navigate, especially in winter. Those using walkers have more bumpy and uneven obstacles in their path, and a person a bit unsteady on their feet to begin with has an increased chance of falling! I personally have a foot issue which causes me to walk gingerly and these raised bump crosswalks are a problem for me, I don’t feel safe, it is harder then to cross the street, and have come very close to falling a few times already! (very recent installation in my town). C’mon, where is our common sense! I am all for aiding the visually impaired, but there should be a way to accomodate all needs.
Link to a page on “PEDSAFE”, an FHWA sponsored organization, that has a list of case studies from various communities around the country on the effects of curb-extension.