Removing Lines as a Traffic Calming Measure: Data, anyone?

Reader Bob Widlansky, from Wilmette, Illinois, writes in regarding a problem on his street that is perhaps the most universal complaint in the world of traffic: Drivers going too fast on residential streets.

As he notes, “I live on a very wide street [pictured above] residential built in the early 1900’s to accommodate a street-car line that used to run down the middle. In an effort to slow down traffic on my residential street, the Village has painted edge-lines and a yellow centerline. The majority of residents believe this has actually increased traffic speeds.”

He has begun pushing the idea (rather unsuccessfully — the city engineer cites safety concerns) at local meetings to remove the center lines, a concept that I describe in Traffic, based on some research done by the TRL and demonstrated in some rural English towns — where it was found that removing the center-lines not only reduced speeds, it led drivers to put more distance between themselves and the opposing stream of traffic. The theory is that lines reduce vigilance, reduce thinking, and potentially increase speeds.

Bob is very passionate about the subject. He’s looking for any data/experience/case studies, preferably from the U.S., where striping and lines were beneficially removed. He’s actually already located some guidance, from the city of Pasadena’s rulebook. He notes that page 22, from the official policy on “Markings/Striping Changes — Removal of Centerline on Residential Streets,” states:

“Centerlines can provide drivers with clear delineation of travelways. On residential local streets that are relatively narrow (36′-42′) with low traffic volumes, centerlines may induce speeding because drivers’ travelways are clearly delineated. Experience has shown that the removal of centerlines on local streets results in more cautious driving behavior. Painted edgelines have a similar effect. Edgelines visually reduce the width of the roadway causing drivers to be more aware.”

I thought I’d open this to the audience: Can anyone help out Bob with studies (before/after observational would be best here, I’d imagine), or have you successfully had lines removed? Or is this even the right way to go about this? Do you have any other suggestions for calming Greenleaf Avenue? Judging by the photo, there are already parked cars, and interestingly, there’s already a sort of differential pavement treatment, a bit confusing to my eyes but apparently not to speeding drivers. What else can be done?

This entry was posted on Thursday, February 12th, 2009 at 1:36 pm and is filed under Etc., Traffic Engineering. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

18 Responses to “Removing Lines as a Traffic Calming Measure: Data, anyone?”

  1. Bob Widlansky Says:

    Thanks, Tom!
    Actually the “differential pavement treatment” is asphalt used to cover pot-holes. Nothing fancy or innovative. :-) The Village claims not to have any significant budget for traffic calming, so even simple stuff like chicanes, gateways, etc. are out of consideration for the near-term.

  2. David M Says:


    Sharrow markings improve lane sharing between different transportation modes and encourage cyclists to ride in safer areas. But notably, they also tend to slow traffic, regardless of the presence of cyclists.
    See: and

  3. Karl-On-Sea (Twitter: @karlonsea) Says:

    Narrow the road, by moving the car parking 1.2m from the sidewalk on each side. Use the space created for a dedicated bike lanes.

    The road width will still be adequate for two-way traffic, but somewhat tighter than it is now – roughly with width of the dark strip of the current road.

  4. Jeroen van Wilgenburg Says:

    On some roads outside the city (in the Netherlands) center lines are removed and replaced by ‘fietssuggestiestroken’ (bicycle suggesstion lanes) to make the road appear smaller. On some roads it’s even impossible to pass each other without crossing those lines.
    The speed limit is lowered to 60 km/h (instead of the usual 80 km/h) and it is believed people slow down because the road appears smaller.

    The pictures of this article show a clear example:

  5. TM Says:

    A lot of material is available on this topic.

    Hans Monderman ( was a leader in the efforts to reduce the over-engineering of streets.

    See also the work of John Adams (, who demonstrated that many “safety” measures, including overengineering of roadways, encouraged greater risk-taking by drivers.

    Here’s a consultant who has done extensive work on neighborhood street design:
    I heard him speak in NYC in 2004:

    Also, check out the UK “Home Streets” concept.

  6. bb Says:

    In Tempe Arizona they have very wide 25mph residential streets which have no stripping or centerline at all.
    Amazing I get passed by the widest margin on these roads.

  7. John Says:

    The Manual on Uniform Traffic Control Devices states the following:
    “Centerline markings shall be placed on all paved urban arterials and collectors that have a traveled way of 6.1 m (20 ft) or more in width and an ADT of 6,000 vehicles per day or greater.”

    I live in Evanston about three miles from this location. Greenleaf in Wilmette is a pretty minor street. I wouldn’t call it an “urban arterial or collector” and I would be very surprised if it carries an average daily traffic volume of 6,000 vehicles. Therefore, it would seem that the lines can be removed.

    Nevertheless, our traffic engineering group in Chicago has used parking lines to visually narrow a roadway and successfully reduce speeds in the past.

  8. MikeOnBike Says:

    [Narrow the road, by moving the car parking 1.2m from the sidewalk on each side. Use the space created for dedicated bike lanes.]

    4 foot bike lanes between the parked cars and the gutter? 100% door zone, with no way to avoid open car doors? No way to turn left? No way in or out midblock except between gaps in parked cars? No way to avoid debris? Um, no.

    As a bonus, the travel lanes would also be in the door zone of the parked cars. Um, no thanks.

  9. Lee Watkins Says:

    This won’t help Bob since they have no operating budget,
    but brick streets with no lines make cars drive as slow as you will ever see, because of the noise and vibrations they produce for the driver. As a result there’s never any accidents here, except on some of the main roads which are paved. They also last at least 50-100 years, compared to about asphalt which needs to be paved frequently at much greater long-term expense. Actually brick streets would be best for a town that has no budget, because they cost less to maintain. You only have to replace the bricks that are cracked every once in a while, and if there’s road work you can reuse the same bricks again.

    This is a street near my house, here in the Greektown/Highlandtown area of Baltimore.

    People rarely get above 15/20MPH. I find that it’s perfectly fine for bicycles if you have an upright sprung saddle, like an old 3-speed Scwinn/Raleigh. These bricks are texturized paving bricks, so people don’t slip on them like you’d see on some newer brick projects.

  10. Bob Widlansky Says:

    Thank you for all the great answers!

    In particular, John from Evanston.. can you please email me at ? I could use your advice.

    You are spot on – there is no reason whatsoever for Greenleaf to have a centerline. To be Village Engineering department is not exactly the most enlightened.


  11. John Says:

    Wilmette has lots of narrow brick, tree-lined streets. They do work great for traffic calming, for everyone except the bicycles with skinny tires like me :)

  12. Bob Widlansky Says:

    The street in question (Greenleaf) was a brick street at one time.
    And Wilmette has a program to restore brick streets.
    The street one block south was just restored recently.
    The problem is (1) the Village idiots removed the bricks for some unknown reason when they did sewer work about 10 years ago, and (2) the Village has no money to fund brick restoration right now.

  13. Big Wayne Says:

    ———- my observation is that the Botts’ dots (on my local freeways ) has decreased lane changes, resulting in slow-moving (relatively…) cars occupying the “fast” lanes . nobody moves to the right – allowing faster cars to pass . . .


  14. aaron Says:

    Before engaging in “traffic calming”, it would probably be a good idea to determine if its a good idea in the first place.

  15. Jim Says:

    @aaron, that’s what a traffic study will determine. Efforts such as chicanes, curb extensions/bulb outs, and speed humps are relatively inexpensive, especially compared to complete repaving projects. Ultimately, the most immediate and cost effective measure might be an increased police presence to enfore speeds, especially during peak traffic periods (rush hours).

  16. Martin Says:

    A low-ish cost solution that they use here in Switzerland is to have periodic constrictions in the road for crosswalks. Because your road is so wide, it would need both inlets from the sidewalk, and a center island. Both of those features could have flowers or shrubbery to look nice. Drivers have to slow down to keep their cars from bashing into the curbs jutting into the road, and they stay slow because the next crosswalk is too close for them to bother speeding up. They often do this trick as you enter a village (sometimes with raised crosswalks that function as speed bumps).

  17. Sam Says:

    I live in Covington, KY on a wide street without any lines; I have been convinced since we moved here that the lack of lines is the primary reason that most drivers obey the speed limit. It is a busy street with pedestrian traffic that almost equals the automobile traffic. Lines only add to the idea that the road is for cars — only cars.
    IMO one-way streets should be eliminated. They destroy neighborhoods and raise speeds.
    Why not create angled parking on one side of the road – this would add space for cars and narrow the road. Most automobiles have a turning radius that would permit entry into the spaces from either side of the road. I suppose that cars backing out into traffic could be a bad.

  18. Tom Bertulis Says:

    Great question – thanks for posting Tom!

    I’m currently doing research on the topic, and I can let you know how that turns out.

    It’s nice to hear everybody’s comments – I just wanted to put in my two cents …

    I can refer folks to before/after studies that point to the benefits (such as reduced speed and reduced crash rate, etc, etc) of removing centerlines. In the UK, there is the study done in Wiltshire County. Just go to this website and do a search for Wiltshire (about half way down.)

    There is also a centerline removal case studies report, focusing on Germany, Switzerland, and the Netherlands. The study is called “Core Traffic Lanes” and can be found here:

    Also information on the Dutch equivalent can be found here, under the section marked Shared Bicycle Lanes:

    Moreover, in August of this year, Minneapolis became the first city in the nation (to my knowledge) to remove centerlines and install “advisory bike lanes.” The bike lanes are six feet wide and the space left over in the middle of the road for two-way traffic is only 14 feet wide. Impressive. I believe this will catch on around the country. Information can be found here:

    By the way, John’s comment above regarding the MUTCD is right on. The MUTCD states that if a road does not have 6,000 vehicles per day then it does not need a centerline. That street in Wilmette most likely does not need a centerline. At the very least, it should be removed to test what the effect is with the option to reinstall it if the community so desires.

    To see the details from the MUTCD, download it and go to Section 3B.01, which clearly spells out current centerline requirements. It can be downloaded from here:

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How We Drive is the companion blog to Tom Vanderbilt’s New York Times bestselling book, Traffic: Why We Drive the Way We Do (and What It Says About Us), published by Alfred A. Knopf in the U.S. and Canada, Penguin in the U.K, and in languages other than English by a number of other fine publishers worldwide.

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