The Traffic Calming Toolbox Post Webinar Q&A

The Traffic Calming Toolbox Webinar


JT- Please speak on the orange pedestrian flags in Salt Lake City. Studies have shown that only 14% of all pedestrians even use these flags, is this a concern?

Although the percentage of pedestrians using orange flags will differ by location within a community and from one community to another, they are undeniably a good safety promotion.  Even their presence in holders on the ends of the crosswalks act as 24/7 sentinels identifying the location/presence of the crosswalk to approaching drivers and warn drivers to slow.


DC- Does a wider speed hump provide for a greater speed reduction as opposed to narrow hump?

No. Typically the opposite is true.  The comfortable crossing speed achieved is the result of the combination of hump height and ramp width. 


DK- where are traffic calming devices typically used on arterials, collectors or local roads. Are there roads that should be avoided for these treatments? Is there volume and posted speed warrants on where they are allowed or not allowed?

Where traffic calming is used is a local decision.  Typically they are used on local and collector streets, not on arterials.  They are also limited to streets with speed limits no greater than 30 or 35 MPH.  Jurisdictions may also want to place a daily traffic volume limit on streets where traffic calming is used.  Basically, the idea is to convince traffic that has alternative routes available to them to use the streets with higher speed limits and classifications and avoid cutting through residential neighborhoods.


DK- Will this presentation be available for download?

The presentation will be available on our website.


JC- We get lots of calls from residents requesting speed humps or traffic calming. How do you determine if a location is a good candidate for traffic calming?

You must first define what you consider to be a problem, such as the extent of speeding or presence of traffic that should be using other streets.  This establishes a threshold as to whether or not an area would qualify for traffic calming.  You will then need to do traffic volume and speed studies to understand what is occurring.  Then, if you believe action should be taken, you will need to decide if the traffic calming tools available to you will be effective.


MB- How can we use traffic calming tools to change driver attitudes?

Once there are sufficient locations in the community where traffic calming devices are being used, drivers begin to understand the level of intent and commitment the community has placed on safe driving.  It’s also important for you and your elected leaders to use your local government public relations tools to educate the public about the purpose and importance of what you are doing.


LM- Any suggestions for parking lot congestion?

Although this is not a traffic calming matter, per se, you will need to study the situation to determine what is causing the congestion.  If there is confusion by drivers on what they need to do to find a parking spot or how to leave, then the answer lies with providing better messaging via signage and/or pavement markings.  If the congestion is simply related to crush loading/unloading, then the answer lies with looking to add an additional driveway or possibly reconfiguring the layout of the aisles and parking stalls or changing the parking payment method.


MC- What are the cost of each of these applications?

You can contact Traffic Logix directly at for price quotes.


RP- Identify cost and maintenance for each use.

Please contact Traffic Logix at regarding cost and maintenance.


PP- What is the cost per square yard of a speed hump?

There is a tremendous range in the costs of traffic calming tools.  For example, speed humps can typically range from $5,000 to $15,000 or more depending on how they are built and how large they are.  Traffic circles can typically range from $5,000 to $25,000 depending on their size, materials and if you are providing watering systems for landscaping.  Bulb outs can typically range from $5,000 to $15,000 per corner depending on their size, material and impact to drainage.  Maintenance is primarily only an issue when landscaping requiring regular maintenance is used.  Some jurisdictions rely on nearby residents to maintain the landscaping.


JS- Are rumble strips an effective traffic calming device?

PM- Can you comment on tactile strips?

Rumble and/or tactile strips are not good for traffic calming.  They are meant for high speed roadways and they usually cause loud sounds not appropriate for residential neighborhoods.


JC- What do you say to citizens who request “children at play” signs?

One response is that no one wants to encourage children to be playing in the street.  If there is a problem with speeding and children do play in the street, you can offer to post a speed limit sign which reminds drivers of the required speed limit as well as assists police in enforcing the speed limit.


RG- How much delay does a speed hump add for emergency services like a typical fire truck?

Just a few seconds per hump.  If this is a concern, the use of speed cushions is a great solution.  It is best if you can talk to your fire department early on about traffic calming and the tools you are considering, then invite them to test their vehicles on/over them in a practice location such as the municipal vehicle yard.  This will help get their buy-in to the program and result in better tools.  Also, if the fire department has designated response streets (usually streets where the fire stations are located that they use every time or most of the time they respond to emergencies); it is usually best not to use speed humps on these specific streets.


BK- What is your experience with traffic radar signs?

They do slow traffic a fair amount initially and then a bit less so longer term.  However, they provide a continual reminder to drivers of their speed and the fact that you and the community believe this to be a street where it is important to not speed.  Depending on the type of driver feedback sign you use, you can also acquire speed data from it and see the actual level of benefit for yourself as well as determine if other traffic calming methods should be used.


JT- Public works departments dislike plowing operations around these devices. How can these concerns be alleviated?

There is no reason snow plows can’t safely and effectively plow over speed humps and around traffic circles, bulb outs and chicanes as long as they are designed for it.  Set up some test radii for circles and bulb outs in a parking lot or on a street using orange traffic cones.  Then invite snow plow drivers, refuse/recycling truck drivers and fire engine drivers to test drive around them.  You will quickly find common ground on what works and what doesn’t.  The drivers may need to slow a bit when negotiating them; but that is the point, as long as they can still accomplish their job.  Working with them helps get their buy-in to the program.


JM- Should speed humps ever be placed in areas where the speeds are higher than 30 mph?

30 MPH is a good upper limit.  You may find a case to use some traffic calming devices on a 35 MPH street, but you will likely need to limit the types of devices used.  For example, you will not want to use speed humps on these streets, but other tools such as intersection corner bulb outs can be safe and effective.


TA- If my HOA wants to install speed bumps or humps, do we have to install warning signs ahead of the bumps/humps? Can you test without signs?

One needs to be aware of the jurisdiction, i.e., owner of the roadway.  If there is an HOA, that typically means the road is privately owned and the maintenance and controls, including the use of speed humps, on the road are the responsibility of the HOA, not the local municipality.  Regardless of the road ownership, it is advisable for the road owner to use advance pavement markings and warning signs when testing or permanently installing speed humps.  Humps should also have markings on them.  Guidelines are provided in several publications including those by the Institute of Transportation Engineers.


CL- Do traffic circles have to have counterclockwise movement? Communities in the NW allowed left turns in front of the circle?

The great majority of traffic circles are designed and signed to only allow counterclockwise movements.  This is the expected movement.  In unusual cases such as where the intersection dimensions are tight and there may be low traffic volumes yet high percentages of trucks or trailers, consideration can be given to allowing left turns in front of traffic circles.  In these cases, it is important to appropriately sign the intersection to warn drivers that this is permissible and which drivers should yield.


TP- If a truck can avoid speed cushions by moving over a few feet, can’t a car do the same thing?

No.  The cushions are located such that the gaps between them fit the wider axle dimensions of fire trucks, buses and other large vehicles.  Typical autos have shorter axles.  Auto drivers will place one set of their tires in a gap, but the other set must travel over the cushion which requires they slow their speed.


RG- How do you address minimum lane widths required by the IFC when “choking down” lane widths? There seems to be a conflict.

If narrow lanes are used, consider placing advance warning signs to indicate their use.  If a specific site is being significantly “choked” consider advance signing to warn drivers of one-vehicle-at-a-time-only usage at the constriction (such as used for one lane bridges).  This is a rare treatment.


MG- In your experience are there documented long term effects of these devices?

When traffic calming devices using vertical or horizontal deflections are deployed, their impact is immediate and sustained for their duration of use.  The affect of driver feedback signs is typically quite good for the first 2 months, then settles into a more sustainable affect that is usually less than the initial one, yet better than without the feedback sign.


JM- What temporary measures are available for traffic calming that can be removed during winter months for snow clearing aside from speed cushions or speed tables?

Flexible rubber curbing can be used to develop traffic circles, bulb outs and chicanes.


LL- Do you have documentation of what speed or intersection configuration a specific device works best at?

As mentioned in the webinar, every location is different, especially when you also consider the volume and composition of traffic at that location and the mindset of drivers.  This is why your evaluation of the situation and discussion with interested parties is important in developing a plan.  And if all possible, test the plan before funding is spent on permanent changes.


AG- When using a speed table as a crosswalk, does it need to be marked and signed as a crosswalk?

This is highly advisable.  It alerts drivers and pedestrians to the use.


JH- Can you address a Neighborhood Traffic Management Program/Manual?

It is advisable that a community with a traffic calming program create a program manual that clearly sets the rules for how it works.  It should contain a process identifying how a neighborhood requests traffic calming, a formula identifying a minimum impact threshold for qualifying for traffic calming and a point system for prioritizing which locations are evaluated first.  It should identify the steps that will be followed in conducting the process from initial request to final disposition.  It should also contain which tools you are willing to use and where (usually by the functional classification/speed of the street).  It should also address funding responsibility and method. 


JC- What is the approximate cost of an average rubber speed hump and rubber speed table?

Please contact Traffic Logix for a quote.


RG- How do you address the concern that bulb outs force cyclists to weave into the motor vehicle traffic lane?

Most jurisdictions legally allow bicyclists the same privileges and rights to use traffic lanes as drivers.  That said, signage such as Share the Road and sharrow pavement markings can be used in these areas if there is heightened concern.  If there is an existing bicycle lane that will be interupted, standard markings and signing can be used to terminate and restart the dedicated bike lane on either side of the bulb outs.


PE- How effective are deploying Slow Signs as compared to speed bumps?

Not very.  You might consider using them as interim improvements until you install speed humps or other traffic calming controls.  However, once you start using them, residents in other neighborhoods will request them.


CS- Are there any standard bus stop locations at roundabouts or other traffic calming?

Far side bus stop locations are usually preferred and safer at intersections whether they have roundabouts or not.  Just as you would provide pull-in and pull-out distance on either end of a bus stop at any location, you will want to provide the same beyond and prior to bulb outs.


CK- I think you mentioned a resource for speed hump design for residential subdivisions. Could you repeat that?

CS- What are resources for raised crosswalk design- especially how curb drainage is maintained.

The Institute of Transportation Engineers and the American Public Works Association provide publications with design guidelines.  You may also wish to review the National Association of City Transportation Officials.  As for maintaining drainage, a good application is to utilize a narrow grate or plate at grade over the gutter/drainage line.  This allows maintenance crews to lift the grate and clean out any blockages that may occur.


MC- Which tools are recommended for narrow roads (ex 20-30 feet wide)?

Speed humps, centerline and edgeline striping work well.  You will be limited in the size of bulb outs that could be used at intersections, but they could work in developing chicanes on alternating sides of the street.  Speed cushions should only be used if their location doesn’t influence drivers to cross the centerline of the street.


MG- Are these concepts effective both during day and night time?

Yes.  It is good practice to provide street lighting and/or other night time delineation at traffic calming device locations.


TA- Is there any comparison data between the effectiveness of using a speed bump on my street vs a light up radar speed sign?

Speed humps slow all traffic to the comfortable speed for which the hump was designed.  A radar-based driver feedback sign merely provides information to drivers to influence them to drive at an appropriate speed, but it doesn’t require speeding drivers to slow.  Thus, speed humps are definitely more effective.


KP- Do you have any examples of chokers that are permanent/curbing rather than just temporary? Also, any specific advice on designing/installing these in a way to make them the most successful at both reducing speeds and not increasing vehicle damage?

Testing choker sizes and locations using flex curbing is highly recommended.  Doing so will provide you valuable input in finalizing a design for permanent curbing/chokers.  All chokers should be sized to not physically intrude on traffic lanes.  They are intended to visually narrow the look of the travel way.  Chokers at intersections should be sized to contain the full width of crosswalks.  Chokers at midblock locations should be sized to define the parking lane.


AL- Will LED speed signs and data retrieval be spoken about as their use in traffic calming?

This will be covered in the February 16, 2016 Traffic Logix webinar.  Save the Date and mark your calendars!


KA- What is the desired speed achieved with the use of a traffic hump? Have your studies revealed that without the use of multiple devices on a single roadway drivers speed up after having gone over the hump?

Speed humps should be designed (combination of height and width) to achieve the desired speed which should be the posted speed limit.  The effective area of speed humps is usually around a hundred feet in advance of the hump and then a couple hundred feet beyond the hump.  Using several humps as well as combining them with other traffic calming devices is considered good practice, especially when calming longer lengths of streets.  The spacing of humps and other traffic calming devices should be such that drivers find it not worth their while to speed up between them only to have to brake hard at the next one.


CS- Are you aware of how autonomous cars react to speed humps? Do they slow down appropriately?

This is a new aspect that bears attention.  It is likely that they will need to be treated similarly to how construction zones will likely need to be treated.  That is, a communication mechanism will need to be deployed in advance of the traffic calmed area to advise the vehicle of their presence.  That said, traffic calming tools are intended to be deployed to allow drivers to travel reasonably and safely at the posted speed limit like any other street.


TE- What is the measured effect of traffic calming on traffic volumes?

This depends on whether or not there was traffic on the street that have route options and should not legitimately be travelling on the street to be calmed.  It also depends on the adjoining street network.  Traffic calming will influence traffic with optional routes to choose another route based on the ease of taking that route.  This is why care needs to be taken in determining if rerouted traffic will be convinced to use collector and arterial streets meant for them or if it will divert to another local street and generate a new unwanted problem.


BI- What would be the advantage of having a rubber speed hump versus that of an asphalt?

Rubber speed humps are typically easier and quicker to install.  They also have a consistent profile.  They also allow testing of locations before permanent installations, whether rubber or pavement, are made.