#42 – Placement of 20-mph School Zone Signs

Seattle, Washington

Megan Hoyt, Pedestrian Safety Engineer, Seattle Department of Transportation


Different jurisdictions across the nation do not use the same policies in determining where school speed zones are established. Not all jurisdictions even use the same speed limit in the school zone. Seattle had experienced pressure from parents and schools to place 20-mph school zone signs as a matter of course in the vicinity of any school. No written policies were previously in place, and most decisions were made on a case-by-case basis. However, certain factors remained constant, including the placement of these signs only at elementary schools, and only in direct relation to a marked crosswalk (in contrast to a set area around the school regardless of crossing facilities).

This project looked at defining and updating current placement of the 20-mph school zone signs (as well as all school crosswalk signs) in Seattle. The goal of studying where to place 20-mph school zone signs was to provide consistency of use for better motorist understanding, and better motorist compliance with the speed limit. A secondary goal was to have better internal guidelines on sign placement to improve consistency of responding to public and school requests for 20-mph school zone signs. The underlying project goal was to reduce driver speeds at the locations where elementary school children were most likely to be walking or bicycling to or from school.

One decision about the placement of the 20 mph speed zone signs was already made by the state of Washington. Locations with a School Patrol present, where there is no form of traffic control, are required to have 20-mph speed zone signs. In Seattle, School Patrol is an optional student program run by the individual elementary school. Participating students are typically in 5th grade and have an adult supervisor. School Patrol members help other students cross safely, but must remain in sight of the school. By contrast, adult crossing guards are adults employed by the Seattle Police Department.

Figure 1. Standard reduced speed school sign.

Combined with this project was an effort to make the 20-mph school zone signs more readily understood as to when the reduced speed limit is in effect and increase motorist compliance. Almost all 20-mph school speed zone signs in Seattle have a qualifying sign attached that reads “WHEN CHILDREN ARE PRESENT” (see fig. 1). This sign is defined through the Washington Administrative Code (WAC) as when:

1) School children are occupying or walking within the marked crosswalk.

(2) School children are waiting at the curb or on the shoulder of the roadway and are about to cross the roadway by way of the marked crosswalk.
(3) Schoolchildren are present or walking along the roadway, either on the adjacent sidewalk or, in the absence of sidewalks, on the shoulder within the posted school speed limit zone which extends 300 feet in either direction from the marked crosswalk.

The general perception in Seattle was that 20 mph school zones are often not obeyed. The Seattle Department of Transportation (SDOT) Pedestrian Program receives a number of complaints from motorists each year asking for clarification of the sign used to qualify 20-mph speed zones. Quite often, the motorist has just received a speeding ticket and is not clear on precisely when the reduced speed limit is in effect. In general, speed zones in Seattle do not receive the respect that parents and school administrators would like to see. The speed at which a motorist travels has a direct effect on the injury sustained by the pedestrian in a collision, and can also increase driver compliance in stopping for pedestrians at crosswalks. A new school zone sign that reads “When Lights are Flashing or When Children are Present” and flashing beacon (figure 2) will replace the sign reading “When Children are Present” and will be set to flash during the times of the day that children are most likely to be traveling to and from school.

The city of Seattle has historically reduced speeds to 20-mph in school zones. The decision of what speed limit to use depends largely on what the normal roadway speed limit is. Almost all arterial streets in Seattle have a speed limit of 30-mph. As the goal of these signs is to reduce motorist speed, the reduced speed should be an achievable change in speed that does not require heavy enforcement. For instance, a reduced speed zone of 15-mph in a section of roadway where the normal speed limit is 40-mph may get very little compliance if it is not enforced. Interestingly enough, however, the city of Tuscon, AZ, has achieved very high compliance in their 15-mph school zones, showing that in the right circumstances this is achievable.

The opportunity for this project occurred as the SDOT upgraded all school crosswalk signs from yellow to fluorescent yellow-green, and changed the school sign at the crosswalk to include an arrow pointing to the crosswalk itself. The field checks necessary to perform the sign replacements presented an opportunity to bring consistency to all school speed zone signs. The pre-existing conditions of each location varied. Fluorescent yellow-green signs were already replaced on principal arterials throughout the city. All other school crosswalks had yellow signs.


Figure 2. Modified reduced speed zone sign used in conjunction with a flashing beacon.


The project itself was three-fold. First, the existing conditions had to be documented.

Second, new School Sign Placement Guidelines were established. Lastly, we implemented the new 20 mph sign policy. During this implementation, a particular location would either:

Additionally, criteria were developed to prioritize where to use the new signs and flashing beacons. In the program’s first year, new speed zone signs with flashing beacons were installed at 12 locations. An additional 14 locations received beacons in 2004. No funding has been identified for further implementation.


To find out what the existing conditions were, a sample survey was taken around several schools. First, we defined the different types of locations possible. The following elements were considered:

While the number of lanes of traffic a pedestrian must cross is an important factor for SDOT when evaluating uncontrolled marked crosswalks, this factor did not play a big role in this analysis. The main reason for this is that few marked crosswalks across more than two lanes of traffic are established as elementary school crosswalks. The speed limit on the roadway also did not play a major role in the survey as only several arterial streets in the city have a speed limit greater than 30. This was a factor in the final decision of where to install the beacons, however.

It was not feasible to survey the entire city (the city of Seattle has over 300 uncontrolled marked school crosswalks alone), so the surveyor sought to find a minimum of five examples of each combination (there were a total of 18 combinations).

Once the survey was complete, we had a better understanding of the existing conditions (see table 1).

Table 1. School Zone Signs Field Survey Totals
# Crosswalks Sampled School Signing Scenario Signs Present At X-Walk Advance Signs Present 20-mph Sign Present End Speed Zone Mid-block crossing
29 Arterial: Marked Crosswalk; No Traffic Control unattended 27 23 5 2 2
17 Adult Guard 16 16 10 3  
8 School Patrol 8 8 6 1  
23 Arterial: Stop Sign unattended 2 0      
3 Adult Guard 2 2 1    
3 School Patrol   1      
20 Arterial: Full Signal unattended 2 2 1    
21 Adult Guard 2 6 1    
5 School Patrol   3 2    
18 Arterial: Crosswalk Signal unattended 4 8 2 1  
8 Adult Guard 6 7 1 1  
3 School Patrol 3 3 3 2  
22 Res: Marked Crosswalk unattended 20 14 9    
0 Adult Guard          
19 School Patrol 17 14 9    
0 Res: Stop Sign unattended          
1 Adult Guard          
2 School Patrol   1 1    

Speed zone guidelines

When the survey was complete, we drafted guidelines that both met the department’s goals of consistency and combined somewhat accurately with existing conditions.

The old 20-mph school zones were inconsistently established. The new guidelines included:

(Maps showing the locations of School Patrol had been outdated; through this process we were able to update some of the locations.) The second priority guideline established was to begin placing 20 mph zones at any uncontrolled crosswalk location with an adult crossing guard present. The philosophy behind this decision was that the adult crossing guards are typically placed at locations where traffic volumes and intersection characteristics are such that students require extra guidance in crossing safely. The locations where adult guards are typically posted also see the highest number of students crossing. Therefore, reducing driver speeds at the locations likely to see the most student traffic focuses attention on the intersections that benefit the most students.

Revised guidelines were discussed among Seattle Department of Transportation staff from the different traffic management divisions. School zone signs were not used at stop- or signal-controlled locations (including crosswalk signals). (See table 2 for placement guidelines.)

Table 2. School Sign Placement Guidelines
School Signing Scenario at marked crosswalks # Signs Present At Marked X-Walk Advance Signs Present R 2M (20mph) Sign Present End Speed Zone
Arterial: Marked Crosswalk
No traffic control
School Patrol Yes Yes Yes Yes
Adult Guard Yes Yes Yes Yes
unattended Yes Yes No No
Arterial: Marked Crosswalk
Stop Sign
School Patrol No No No No
Adult Guard No No No No
unattended No No No No
Arterial: Marked Crosswalk
Full Signal
School Patrol No No No No
Adult Guard No No No No
unattended No No No No
Arterial: Marked Crosswalk
Crosswalk Signal
School Patrol W-37overhead sign only No No -
Adult Guard W-37 overhead sign only No No -
unattended W-37 overhead sign only No No No
Residential Marked Crosswalk
No traffic control
School Patrol Yes Yes Yes Yes
Adult Guard Yes Yes Yes Yes
unattended Yes Yes No No
Residential Marked Crosswalk
Stop Sign
School Patrol No No No No
Adult Guard No No No No
unattended No No No No

Flashing beacons

In prioritizing the flashing beacon locations, we used the above criteria and also considered average daily traffic (ADT), with higher ADT locations receiving a higher priority. For more consistency with standard engineering practice, and because of the weekday-only nature of the flashing beacon signs, the list of selected locations also includes the most current Average Week Day Traffic (AWDT).

A recent study released by the Federal Highway Administration notes the factors that influence pedestrian safety at marked crosswalks (Zegeer et al., 2002). These are the number of lanes of motor vehicle traffic, the average daily traffic (ADT) and motor vehicle speeds. To select the final 12 locations, staff at the SDOT evaluated all marked crosswalks qualifying for a 20-mph school speed zone. None of these locations had more than two lanes, and only a few had a speed limit higher than 30 mph. Therefore, the locations were ranked by ADT.

Twelve locations ranked highest on selected criteria for the first year of implementation. All locations had adult crossing guards posted. While almost every marked crosswalk considered for this treatment was an uncontrolled marked crosswalk, there were several locations that had crosswalk signals (also referred to as half-signals). One of these locations had not only very high ADT and high vehicle speeds, but also was a high complaint location. This location also was on a roadway with a speed limit of 35-mph. For that reason, it was included in this list of the top 12 locations. The subsequent year of beacon installations used the next 14 locations on this same list. Two locations on the list were not implemented due to construction and timing issues.


With guidelines in place, sign replacement, including the establishment of new 20-mph school zones, was begun. Signs on minor and collector arterials were replaced in 2002. Signs on non-arterial streets were replaced in 2003.

The installation of the flashing beacons required utility poles on which to mount them. All beacons were installed on the side of the road approximately 200 feet in advance of the marked crosswalk. In several cases, it was possible to use an existing pole. However, the majority of locations required the installation of a new pole. Due to restrictions in where a utility pole could be installed, or existed already, some of the school speed zone boundaries were altered. All efforts were made to place the zone limits as close to the MUTCD guidelines as possible.

Evaluation and Results

Defining specific evaluation criteria was difficult for this project because we did not know until halfway through which locations would change and which would stay the same. There is also the fact that all locations were being upgraded to the fluorescent yellow-green school signs, which complicated the effect the 20-mph speed zone alone would have.

Therefore, the evaluation could best be examined in terms of public feedback and internal opinion. Positive feedback came from the adult crossing guards themselves because quite a number of them did not have the reduced speed zone signs at their locations. This project also created consistent guidelines for 20 mph zone establishment, and has resulted in clearer communication to the public about where the signs are placed and the reasons for the particular sign placement. There have been some negative comments from citizens, however, who wonder why the school speed zones are being established at the locations with an adult crossing guard rather than the ones that lack a guard. This particular complaint requires ongoing explanation of the advantage SDOT sees in focusing attention on the places where the most children cross, and where (through placement of an adult crossing guard) it has been determined that children need more guidance in crossing safely.

Before/after speed assessments were performed for several of the flashing beacon locations to determine if motorist compliance increased. The before measures were taken in spring 2002 for most locations, as project completion was originally scheduled for August 2002 (actual construction occurred in August 2003). The before results showed a clear disregard for the 20-mph school speed zones. ‘Before speeds’ when children were present ranged from 32 mph to 40 mph.

Speed data were also collected several months after the signs and beacons were installed. In all but one case, vehicle speeds when an adult crossing guard was present were lower following installation of the new signs and beacons. The largest decrease in speed noted was a 22 percent decrease (the 85th percentile speed dropped from 37 mph to 29 mph). Despite the reduction in vehicle speed, the range of speeds measured (29 mph to 34 mph) were still well above the 20 mph speed limit.

Conclusions and Recommendations

The SDOT relied directly upon the placement of crossing guards in sign placement. Other jurisdictions may want to consider other criteria in the placement of 20-mph speed zone signs. Criteria that could be considered include the distance from the crosswalk to the school and the number of students using the crosswalk. An important detail to keep in mind is the amount of annual survey work that must be conducted to keep signs current. While the number of students using the crosswalk is important, collecting this information for hundreds of crosswalks could be a large task.

It was very useful to do the survey work and create guidelines for sign placement throughout the city. It is an excellent way to gain internal concurrence on guidelines and to take time to verify that current practices are still useful.

It is not clear whether the consistency of the signs has been noticed or appreciated by the public. In most cases, residents are happy if the change in guidelines allows a school speed zone to be established at a crossing they often use.

While the speed study analysis did not show as large a drop in vehicle speed as we would have liked, it did result in reduced vehicle speeds within the reduced speed school zones. A notable result of the new beacons has also been more effective enforcement by the SDOT. Officers are given a list of the beacon locations and the times they will be in effect. Targeted enforcement is therefore possible, and the SDOT keeps a log of the times the beacons flash which reduces the number of motorists who can contest a ticket.

Costs and Funding

The upgrade of the school crosswalk signs was funded through state grant funding. The survey work and background gathering necessary for this project were made possible by help from a graduate school intern and a transportation crew worker on light duty. The first year of flashing beacon installation was funded by a state grant, and the second year was funded by the Seattle Department of Transportation.


Zegeer, C.V., J.R. Stewart, H.H. Huang, P.A. Lagerwey, J. Feaganes, and B.J. Campbell. Safety Effects of Marked Versus Unmarked Crosswalks at Uncontrolled Locations: Final Report and Recommended Guidelines. Federal Highway Administration, Office of Safety Research and Development: McLean, Virginia, February 2005, 110 pp. [FHWA –HRT-04-100] available at: http://www.walkinginfo.org/pdf/r&d/safetyeffects.pdf


Megan Hoyt
Pedestrian Program
Seattle Department of Transportation
700 Fifth Avenue, Suite 3900
Seattle, WA 98104
(206) 684-5124

Peter Lagerwey
Bicycle & Pedestrian Program Coordinator
Seattle Department of Transportation
700 Fifth Avenue, Suite 3768
P.O. Box 34996
Seattle, WA 98124-4996
(206) 684-5108