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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  • Share: Sharing our content on Facebook, Twitter, Pinterest or any other platform helps you share what’s important and casts a wider net for our audience. So Tweet, Like, and Pin until your hearts content.  Also, guaranteed karma points.
  • 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.
  • Remember the URL: Definitely the most low-tech and good for memory! Just type in the URL to check and see if new content is up.

Thanks for supporting safe streets in Bellevue and beyond!

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NE 5th Street to Close for 3 Weeks; Starts Monday


Construction along NE 5th Street will close the roadway 24/7 for approximately three weeks.

Construction in the Wilburton neighborhood along NE 5th St between 120th Ave NE and 124th Ave NE is set to begin today (Friday, April 26).  On Monday, April 29, construction work will ramp up requiring the roadway to be closed in both directions until mid-May, weather permitting.

The closure of NE 5th St will allow access to properties on NE 5th St and the cul-de-sacs of 123rd Ave NE and 123rd Pl NE.

To help expedite this construction, the work will continue through the weekends. Please drive safely and obey flaggers through and around the construction zone.

The NE 5th Street Neighborhood Traffic Plan includes a one-lane zone, a crosswalk on 124th Avenue NE at NE 5th Street and landscaped medians on NE 5th Street east of 124th.

Follow @BvueTrans on Twitter for updates.

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New Real-time Traffic Map Released

The City recently released a new, spatially accurate real-time traffic map to provide residents and visitors with another way to make informed travel decisions.  The map, based in Google Maps, overlays 75 traffic cameras through the City and capitalizes on the familiar color-coded traffic conditions (black/red-red-yellow-green) used in Google Maps to depict congestion levels.

The new real-time traffic map has a familiar Google Maps interface and combines current traffic conditions with more than 70 traffic cameras situated around the City.

The new real-time traffic map has a familiar Google Maps interface and combines current traffic conditions with more than 70 traffic cameras situated around the City.

The map features convenient views that focus on the entire City or some of the most traveled parts of town such as downtown, Factoria/Eastgate, and Crossroads.  Additionally, through the use of layers, users can quickly link to other adjacent Eastside and regional traffic maps including Issaquah, King County, Redmond, Seattle, and WSDOT. 

In addition to viewing Bellevue traffic and traffic cameras, you can quickly jump to other regional traffic maps.

In addition to viewing Bellevue traffic and traffic cameras, you can quickly jump to other regional traffic maps.

Releasing the map precedes the start of a busy construction season around Bellevue.  Many projects from Transportation, Utilities, and Parks are currently underway or will be shortly. For example:

  • Construction on West Lake Sammamish Parkway began earlier this year resulting in increased congestion during certain times of the day. 
  • In May, the Utilities Department will begin work on replacing the Coal Creek Culvert  which will reduce travel lanes down to one in each direction.

Checking the map before you leave home or work will help you to plan a more time-efficient trip, especially as projects transition from design to construction. 

Checking traffic before you leave will help you to avoid congested areas like this stretch of West Lake Sammamish Parkway which is currently under construction.

Checking traffic before you leave will help you to avoid congested areas like this stretch of West Lake Sammamish Parkway which is currently under construction.

To learn more about projects that are sprouting in Bellevue, come to the April 24 Spring Forward Expo where 60+ projects will be on-hand to share information and gather public feedback.  The event will be at Bellevue City Hall from 4-7 p.m.

In addition to checking the real-time traffic map, be sure to subscribe to traffic advisories and follow @BvueTrans on Twitter.

You can access the map from the front-page of the City of Bellevue website.

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Radar Signs Installed Ahead of March 19 West Lake Sammamish Parkway Detour

At this point, the West Lake Sammamish Parkway (WLSP) southbound detour from SE 34th Street to I-90—scheduled to commence March 19 and last approximately 8 months—should come as no surprise.

While the closure will impact commuters and residents by potentially adding a few minutes to their trip, neighborhood residents adjacent to the detour area will deal with other effects from increased volume traveling on their streets.

To address increased volume and to remind drivers of the posted speed limit, NTSS recently installed 4 new stationary radar signs along SE 34th Street, 164th Place SE, and SE 38th Street.  Stationary radar signs display motorist’s speed and, if necessary, alert driver’s to reduce their speeds if they are exceeding the posted speed limit; the speed limit is 30 mph along SE 34th Street and 25 mph along 164th Place SE and SE 38th Street.


This radar sign on the north side of SE 34th Street just west of West Lake Sammamish Parkway was installed prior to the March 19 detour.

This radar sign on the north side of SE 34th Street just west of West Lake Sammamish Parkway was installed prior to the March 19 detour.

There had been an existing radar sign located on 164th Place SE south of SE 34th Street.  This sign, one of the first of its kind installed in the City, was positioned in such a way that its visibility was hindered by encroaching vegetation and the curve of the street.  With this installation, the sign was removed and relocated farther south where it will be more visible and thus effective at slowing southbound drivers.

WLSP Detour  


The southbound WLSP detour will begin Tuesday, March 19.  Access is limited to as far south as SE 34th Street.  Northbound access will remain open along with local access to businesses, schools, and recreational activities.  Though the northbound lane will be open, delays are still possible.  The 8-month southbound closure is necessary to expedite the completion of the project.  If both lanes were kept open, the construction timeline would double to 16 months.

Follow us on Twitter to stay updated as the detour starts.


Additional Resources:

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