You Say Speed Bump I Say Speed Hump

In 1906, a small town in New Jersey officially and successfully installed the first recorded speed bump. The town of Chatham used the ‘speed reducers’ to alert cars to pedestrians using crosswalks. On the day they were tested, hundreds of residents gathered around the bumps to watch the ‘machines’ drive across them. The bumps, which were 5 inches high and made of rock and clay, gave the first motorists to traverse them quite a rude surprise when his car shot up several feet. This solicited a loud cheer of approval from all those watching and proved that the speed bumps were in fact effective. We should all take a moment to thank modern suspension for being able to handle speed bumps a little better than Fords model A’s, C’s, and F’s.

Today the term speed bump is often used to refer to a family of vertical deflection devices. Within the family there are variations of the speed bump, a hump, and a cushion.


Identifying the Vertical Deflection Devices
Speed bumps are the most commonly used form of vertical deflection devices. Due to speed bumps height (3-4 inches) and their width (usually 1 foot), they are designed to slow vehicles down to about 5 mph, which makes them ideal for parking lots. The City of Bellevue does not install this type of device.

Speed humps, originating in England, are more convenient for residential roads where the intent is to slow cars down to about 15-20 mph. They tend to rise up to about 3-4 inches but do so over a much broader distance. They are usually 12-22 feet in length and span both lanes. Speed humps were designed in the 1970’s as an alternative to speed bumps so that emergency response vehicles response time wouldn’t be as impacted when responding to an accident. The City of Bellevue uses speed humps that are 22 feet in length on emergency response routes, used for raised crosswalks, in areas with transit routes, and  on roadways have that have higher traffic volumes. Wondering why speed humps are not labeled as speed humps (versus speed bumps) in the City of Bellevue? Well, it’s a commonly stolen sign.


A speed hump is placed in a residential neighborhood adjacent to downtown Bellevue, WA

Bellevue also uses what is called a split speed hump. This is where the speed hump is split into two sections. Each section crosses the entire lane but they are placed several yards down the street from each other. This allows emergency response vehicles to navigate between them instead of over them.

A speed cushion is similar to a speed hump but instead of being a single bar across all travel lanes it is cut into multiple sections. The middle section is six feet wide with one foot slots between the outer sections. This allows vehicles with wider axles such as emergency response vehicles to drive through the slots without having to slow down.

Speed Humps Comparison

Sleeping Policeman: United Kingdom, Judder Bar: New Zealand, Band of Breaking: Mexico

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Grind and Overlay

‘Tis the season for construction projects and at the top of the list each summer is repaving projects. With more sun, longer days, and fewer cars on the roads, it’s prime time for construction crews to head out on many roads to repave and make repairs.


The City of Bellevue will be attending to approximately 22 miles of Bellevue streets this summer. The video below gives an overview of the Streets Overlay program and how the grinding and overlay process works.

The City of Bellevue has also put together a page dedicated to informing you of upcoming projects so you can be aware of whats happening. Remember, part of the paving process involves putting temporary rubber locators in the roadway to identify utility lids.

Finally, there is a great animation and explanation of grinding/overlay over at Pavement Interactive. The website walks you through the different procedures that occur between the grinding off of the old asphalt and the placing of the new layer.

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Rectangular Rapid Flashing Beacons in Bellevue

The project team (the "Fab Five") for the recently completed NE 8th St RRFB at Crossroads Park walks across the mid-block crosswalk.

The project team (the “Fab Five”) for the recently completed NE 8th St RRFB at Crossroads Park walks across the mid-block crosswalk.

As the city grows, so does our transportation technology toolbox.

In the past few years, the City of Bellevue Transportation Department has introduced new intelligent transportation systems such as flashing yellow arrows (FYA) and adaptive signal controls.

While those technologies focus primarily on the motorist, new rectangular rapid flashing beacons (RRFB) are providing pedestrians with increased visibility at crosswalks where there are not otherwise signals (e.g. mid-block crosswalk).

Not sure how to use crossing locations that use RRFBs? Check out this video:

RRFBs are slowly rolling out to select locations in Bellevue. RRFBs are signals that are push-button initiated by the pedestrian that activate rectangular LED flashing lights above the roadway informing motorists that pedestrians are in the crosswalk. Unlike at signalized intersections, pedestrians won’t receive a “Walk” phase. As a result, you should still proceed cautiously across the street when traveling across roadways with traffic approaching.

As a motorist, according to Washington state law you have a responsibility to watch for and allow pedestrians to cross the roadway, regardless of whether the pedestrian is at a marked or unmarked crosswalk at the intersection.

Why use this technology?

RRFBs, when compared to traffic signals, are a lower-cost alternative and have been found to increase motorist compliance compared to other technologies. Federal studies indicate that RRFB’s irregular flashing patterns create higher driver yield rates to pedestrians than other the treatments; the flashing pattern is similar to flashers on emergency vehicles. RRFBs increase attention to mandated signage for mid-block crosswalks. In that way, they are an “above-and-beyond” measure intended to increase visibility for pedestrians trying to traverse busy roadways.

While RRFB technology is relatively new to Bellevue, its use is becoming more commonplace with new locations being evaluated on a regular basis. However, much like the flashing yellow arrows, pedestrians and motorists will likely need some time getting accustomed to this new technology.

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Traffic Lingo A to Z: Channelization

As with any field, sometimes we transportation professionals can use jargon terms that you may have heard but are not that familiar with. To clarify these terms, we have been publishing a twice-weekly Twitter feature on @BvueTrans to define them.

While 140 characters is great for some terms, sometimes we need a little extra room to explain a term here on Streets are for Everyone. Enter: channelization.

  channel labels3 This intersection in downtown Bellevue at NE 8th St and 112th Ave NE uses several different methods to channel traffic including medians, lane markings, curbing, islands and raised pavement markings. The purpose of these devices is to separate competing traffic flows.

At this intersection channelizing islands funnel traffic turning right allowing traffic to move quickly through the intersection. This intersection includes pavement markings that decrease the angle at which cars are merging onto NE 8th St allowing them to merge more effectively at higher speeds.

Raised pavement markings, accompanied with painted lane markings, guide moving traffic through this intersection. Raised pavement markers easily communicate with drivers where they should drive and alert drivers if they cross over by vibrating the vehicle.

Crosswalk markings help both pedestrians and vehicles identify safe crossing areas. Though not shown above, bike lane markings are used to create delineated space for cyclists in the roadway. Sharrows are bike markings placed in the travel lane to identify where cyclists may be traveling in the roadway. If you missed our previous #trafficlingoAtoZ tweets, check them out below. 

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Black Rubber Tubes in the Roadway: Helping to Understand Your Neighborhood

As the New Year begins, Neighborhood Traffic Safety Services will be conducting several new traffic studies that measure vehicle speed and volume in Bellevue’s neighborhoods. These studies are an integral component in how we analyze a street to determine traffic conditions.

tubes stretched across roadway

The presence of two tubes across the roadway indicates that both speed and volumes are being recorded. If only one tube is present, that’s an indication that only volumes are being recorded.

With holiday travel behind us and school back in session, now is a great time to study our neighborhood streets for representative speeds/volumes. Do we send a staff member in the field to guess how fast cars are going? Of course not (our perception of vehicle speeds is usually very different from reality), we hire a consultant or use in-house staff to set a series of pneumatic tubes across the roadway that accurately and reliably capture both speed of individual vehicles and also aggregates how many vehicles pass over the tubes into daily counts.

Perhaps you’ve seen these black rubber tubes on neighborhood streets or on arterials. Seemingly low-tech, these tubes collect vehicle data over time (we usually conduct 7-day counts to ensure we understand the difference in travel behavior during peak weekdays, usually Tuesday through Thursday, while also including the weekend; typically, there is a steep drop-off in vehicle volumes between weekday and the weekend).  Here is how speed studies are generally conducted:

  1. A street is selected for the speed/volume study by city staff or a resident. The street is analyzed for the best place to place the tubes; generally, mid-block locations away from intersections or other obvious impediments that aren’t representative of the streetscape are preferred.
  2. The tubes are nailed into the roadway by a trained technician. Precise, parallel placement of the tubes is critical to ensure accuracy.
  3. Vehicles travel over the tubes for the duration of the study. As vehicles travel over the tubes, blasts of air are sent to the receiver box and the data is stored in the box until the technician picks up the equipment.  With a known distance between the parallel tubes, speeds are calculated by measuring the time difference between the front axle hitting the first and second tubes.
  4. After the field component is completed, the technician retrieves the equipment and compiles the data to send to staff.
  5. Staff receive the data, interpret the results, and communicate a summary to residents (often in the form of a Traffic Action Plan).

Though traffic studies are important in understanding conditions on the roadway, it’s by no means the only step in determining whether there is a traffic safety issue.  The studies are a first step that complement other analysis that create a holistic view of what is going on in the roadway.  However, that’s not to say we haven’t collected a lot of data in the city over the years…

Speed Study Locations

Each blue square represents the location of a where a neighborhood speed and/or volume study was conducted in Bellevue.

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We’re Ready for Winter Weather. Are You?

Take Winter by Storm Logo

Be sure to Take Winter by Storm this year. Stay in the know with closures, tips, and updates!

Well, aside from some rain over the passes, we escaped the Thanksgiving holiday with minimal travel disruptions. Calmness in November, however, does not indicate calmness for the rest of the winter months. 

In the coming months when you are out and about—whether it’s a quick trip to the store or up to the mountains—be prepared for winter weather anytime, anywhere.

Last year, we posted some tips on how to best prepare for winter travel and what you should take with you when traveling.   This year, we want to reinforce and remind you that traveling in snow/ice takes planning, awareness, and caution. Remember, the best way to traveling during winter conditions is to avoid travel altogether.

When you are in Bellevue…

ExtremeWeather_SmallBe sure to sign up for the City’s extreme weather response alerts. Each time this City webpage is updated, you will receive either an email or text alerting you to the change.  This is the best way to see how the City plans to or is responding to extreme weather.

If you must travel, check the snow response priority map to plan your route along roadways that are more likely to be freshly plowed and check the real-time traffic map to see how traffic is flowing throughout the city.

If snow/ice hits, the city’s Twitter feeds will be pushing out information to our followers with road conditions, response efforts, and general updates (City, Transportation, Police, Fire, and Emergency Management).  Check for school closures on

King County has great resources with tips on how to prepare for snow/ice and how to drive when the weather gets nasty.

Heading out of town…

While avoiding travel is best, who can resist the call of fresh powder in the mountains? Fortunately, there are plenty of resources outside of Bellevue to help you get you where you need to be when conditions get dicey.

If headed to the mountains, consult WSDOT’s pass report on Twitter (Snoqualmie, Stevens, Blewett, White). There, you can see whether there are travel restrictions, view real-time cameras, and check the mountain forecast).  When traveling, you can always call WSDOT’s 511 to get location-specific updates on road conditions.

This year, WSDOT introduced an easy-t0-read infographic reminding you what to have in the car when traveling during winter.  Do your part and be prepared for whatever comes our way this winter.


Regardless of whether you are traveling near or far, always be prepared for potenially hazardous conditions.  Check conditions, keep informed, and stay safe.

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What are Chicanes?

chicane-defChicanes–or slow points–are horizontal deflections designed to slow traffic speeds and can potentially discourage cut-through traffic.  They interrupt a normally straight roadway forcing drivers to reduce their speed and navigate the chicane before continuing down the roadway.  Chicanes are just one tool the City of Bellevue utilizes to address neighborhood traffic concerns.

Still not sure what a chicane is? This animated video will paint a clearer picture.

You might have noticed a chicane in the Wilburton neighborhood on the crest of 128th Ave NE just south of NE 5th St (below) or on NE 5th St between 120th Ave NE and 124th Ave NE.  Neighborhood Traffic Safety Services is exploring installing a double chicane in the Enatai neighborhood along SE 8th St.  Depending on their application, chicanes are either stop-controlled (like on NE 5th St) or simply instruct motorists to yield to oncoming traffic (like on 128th Ave NE).

The roadways narrows allowing for only one motorist to pass through at a time. While it seems obvious that you simply drive through the delfection when you encounter a chicane, driving through when there are multiple vehicles waiting becomes trickier. Driving chicanes when there are muliples cars queing is like driving a one-way bridge: wait for all the opposing traffic to clear, then carefully proceed through the chicane. Once your vehicle and the motorists behind you are through the opposing traffic will pass and continue the cycle.

Think parking is bad in Bellevue? It’s nothing compared to New York where chicanes naturally form when cars are double-parked.

Safe driving!

More information:

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School buses: Red lights flashing? You should be stopping!

In Bellevue, school buses traverse the City in the mornings and afternoons picking up and dropping off children to 16 elementary schools and 5 middle schools (high schools utilize King County Metro). At any given time while driving, you may encounter a bus with red lights flashing and the stop sign or bar out signifying that children are either getting on or off the bus. On a two-lane road, everybody must stop when this happens. But what happens when traveling on a three-lane road or a road with a median?

Follow our handy graphic to learn when you should stop if you encounter a bus with red flashing lights on.

Passing School BusesWhen to stop for school buses?
1. 2-lane roadway: both directions stop
2. 3+ lanes: stop if traveling same direction as bus
3. Turning lane: stop if traveling same direction as bus
4. Median: stop if traveling same direction as bus

Thinking about not stopping for a school bus when the red lights are flashing or the stop bar is out? Be prepared for a $394 fine. Traffic enforcement officials need not be on-hand to enforce the infraction; bus drivers are trained to document infractions which are admissible in a court of law.

If you’re still uncertain about when to stop, check out this video from the Washington State Patrol—it contains all the vital information (including reinforcing the $394 dollar fine!).

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Back to School Edition: 2013

Image courtesy of Flickr user tncountryfan

Image courtesy of Flickr user tncountryfan

Pencil boxes are fully stocked, brown bag lunches carefully arranged, and a new pair of sneakers can only mean one thing: back to school time!  Though school started last Tuesday, we are still hearing comments from parents and residents about congestion around schools, especially elementary schools.  To help you ease into and prepare for the school year, below are resources offering traffic safety tips, updates, and upcoming events!
Check out last year’s Back to School edition!

Traffic Safety Tips:

Whether you are driving, walking, biking, or taking the bus, please exercise caution and travel safely.

  • Slow down
  • Pay attention while driving; don’t be distracted by using electronic devices or cell phones
  • When beacons are flashing or children are present the speed limit is 20 mph
  • Stop for pedestrians and children getting on and off school buses
  • Remember to be aware of your surroundings while turning or changing lanes
  • Stop completely at all intersections
  • Pedestrians should use crosswalk

School Fines Doubled in Elementary School Zones

Did you know fines double in school zones?  Around elementary schools when children are present or when yellow beacons are flashing, you are subject to higher fines when cited speeding or other moving infractions.

164th South of NE 24th BSchool Zone Flashing Beacons Coming to 3 Elementary Schools

Speaking of school zone flashing beacons, you have probably seen them around Bellevue and Issaquah (Cougar Ridge and Sunset Elementary Schools are part of the Issaquah School District but located in Bellevue) elementary schools.  The list that has beacons is increasing this year as the City received state grant funding to install beacons in three new locations: Cherry Crest, Cougar Ridge, and Bennett elementary schools.  Installation should occur before the end of the year.

Generally, the flashing beacons begin to flash about a half hour before school starts and continues for 10 minutes after the first bell (see full schedule).  The beacons resume flashing in the afternoon 10 minutes prior to dismissal time followed by an additional 30 minutes.

Walking School Bus

A walking school bus can make your commute smoother and also encourage children to lead a more active lifestyle.  A walking school bus is a group of children walking to school with one or more adults.  Volunteers in the neighborhood work with one another to create a schedule and timetable of all the planned meetings spots.  Much like waiting for a school bus, children wait at their designated stop until the walking school bus arrives.  They then join the walking group and pick up more students until they reach the school.

WalkToSchoolDay_LogoWalk to School Day 2013—October 9

Walk to School Day is on October 9 when schools all over the world encourage children to Walk to School that day. This year, the City will be coordinating with elementary schools to set up activities that may increase visibility and accessibility of children walking to school.

This year, the City of Bellevue is coordinating with Bellevue School District Elementary Schools to plan for Walk to School Day.  If your school agrees to participate, additional information about Walk to School Day events will come directly from your school or PTSA.

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Keeping in touch!

If you access this blog via Google Reader, you are probably aware that on July 1, Google is discontinuing this service. That means you need to find other ways to get here!

Fear not, for there are many other ways to make sure you don’t miss out any content.

  • RSS Feed: Obviously if you were a Google Reader user, then you know this blog (and every blog) is RSS enabled. So just subscribe using any aggregator or reader that isn’t, you know, Google Reader.
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  • Bookmark/favorite: A low-tech favorite! Go ahead and favorite or bookmark the URL.
  • Follow us on Twitter: The Bellevue Transportation Department is on Twitter! Each new story on SAFE gets tweeted so you never miss a beat.
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Thanks for supporting safe streets in Bellevue and beyond!

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