***30 km/h ≈ 20 mph***
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The Netherlands made it possible for municipalities to create 30 km/h zones starting in 1983. This became a great solution for making neighborhoods more livable and happier by reducing daily traffic and lowering speeds of cars(so the kids can play!). This was beneficial not only to residents, but also to governments because they began receiving a rebate for creating 30 km/h zones from the national government. According to the Institute for Road Safety Research(SWOV), 30 km/h zones tend to be very safe, decreasing the number of crashes by 25% compared to 50km/h zones. Also, the likelihood to survive as a cyclist or pedestrian is still fairly high when speeds are low(see Fig 1). There are .1 crashes with injury per 106 car km in 30 km/h zones.
Figure 1—Graph showing probability of death in vehicle-pedestrian crashes
I was tasked with studying 30 km/h zones in the Northwest section of Rijswijk, Netherlands. The area is split between 8 neighborhoods and each utilizes different tactics to maintain 30 km/h zones through the neighborhood streets. Some neighborhoods have more comprehensive speed control, while others, such as Presidentenbuurt neighborhood, are lagging a bit behind. Overall, the success of 30 km/h zones can be broken down into 3 main attributes: entry treatments, speed control within the zones, and road function.
To be successful, the measures taken to reduce the speeds of cars must be self-enforcing, meaning drivers will automatically go the speed limit/ obey intended road function based on road design. It is uncomfortable to not do so under any circumstances. A simple sign is not sufficient and relies too heavily on the goodwill of drivers. Relying on signs makes for a less forgiving design because driver mistakes are not mitigated, and they do not catch human error. This is why the Dutch make their speed limits self-enforcing and their local roads inhospitable to through traffic.
The United States could learn a lot from the 30 km/h zone methodology. Safety and comfort are universally sought, so it would be in many American neighborhoods’ best interest to adopt a strategy to self-enforce low speed limits in residential areas. I will identify one Colorado neighborhood in particular that could greatly benefit from 30 km/h zone methodology.
Entry treatments, such as crossing tables/raised crossings, grab drivers’ attention right as they enter a neighborhood and physically force the car to slow down by forcing a large jolt. To avoid discomfort, drivers will naturally slow down. This trait makes entry treatments a great way to declare entrance into a 30 km/h zone.
|Treatment||Purpose||HOW it works||Comments|
|Crossing table||Slow cars, grab attention||Jolts cars, causes discomfort||Very effective|
|SIgnage||Make drivers realize speed limit||Drivers see sign and behave accordingly||Not the most effective, relies on mistake-prone drivers|
|Cycle/Pedestrian priority||Slow cars, make them 2nd tier||Cars waiting for bikes and pedestrians sends the message that cars are not prioritized. Also, cars physically have to slow their speeds and watch for pedestrians and cyclists.||Every neighborhood entryway does not give priority to cars|
Speed control within the zone
Now that a driver is inside of a zone safely thanks to entry treatments, road designers must make sure their speeds are kept low within the 30 km/h zone. The table below explains commonly used measures in Rijswijk.
|Treatment||Purpose||HOW it works||Comments|
|Speed hump||Speed control/awareness||Give drivers a jolt by forcing their car upward. At high speeds, hump can cause liftoff from ground/bumper hitting ground||
|Brick pavement||Speed control/awareness||Rougher terrain/ increased vibration = more discomfort, more discomfort=slower speeds; recognition of residential area||Nearly all 30 km/h roads in Rijswijk have the same brick pavement. This continuity increases predictability & recognizability.|
|Raised intersection||Speed control/awareness||Grabs attention with small rise. Puts drivers at pedestrian level, making them more aware||Mitigates mistakes, reduces approach speed, and increases safety at possible conflict point. There is one at most conflict point(even car-bike/ car-ped)|
|Chicane||Speed control/awareness||Forces a curving maneuver which is uncomfortable at high speeds||Drivers went very slow around these. Worked very well in combination with speed humps|
|Slow sign||Speed control/awareness||Make drivers think twice about speed||Not very effective, but cute. More suggestive|
|Pavement paint||Speed control/awareness||Make drivers think twice about speed||Not very effective, but cute. More suggestive|
Through routes are routes in which neither a car’s origin or destination is along the route. Because the drivers’ “A” and “B” are not along the route, they tend to drive faster to minimize transit time. This makes such a road function incompatible with 30 km/h zones and local roads. In order for a 30 km/h zone to be successful, it must not be attractive to through traffic, cut throughs, or rat running. Rijswijk has utilized many measures to eliminate through traffic from the neighborhoods. Also, shopping access is incompatible with through traffic, and you see many shops in these local Rijswijk neighborhoods, further proving their efforts to make their roads functionally harmonious.
|Tactic||Purpose||HOW it works||Comments|
|Entry treatments and speed control||Make cutting through slow and unattractive||By significantly slowing cars journeys, cars know not to use local roads as a cut through||There is a crossing table at nearly every point a higher level road meets a local, 30 km/h road.|
|Street layout||Inconvenience||Disallowing grid-style traveling. Make traveling weave and turn often.||By eliminating straight through routes and designing neighborhoods in a way that makes them more curvy, through traffic is discouraged|
|Permeable barriers||Inconvenience||Disallowing through car traffic||Does not disturb bicycle and pedestrians connectivity|
|Alternating one ways||Inconvenience||A road gets killed halfway through by having oncoming traffic does not allow cars to drive the whole way||Very effective|
The biggest deterrent to cycling is traffic stress. In order to bicycles and cars to safely share a road(cyclists and cars will never share a lane), the roads must be unlaned. A bicycle will never share the road with a car in a place that the cars don’t already share it with one another. To further increase the safety of cycling in mixed traffic, an average daily traffic(ADT) should ideally be less than 2000 because this means there is a lot of time between cars. In the Rijswijk 30 km/h zones, all cycling is in mixed traffic, and the nearby access roads have different treatment. See the table below.
|30 km/h zones||Mixed traffic||Low volume, low speeds. Less chances for conflict, more chance of survival in crash||Cycling in the 30 km/h zones was very comfortable, but there weren’t all that many cyclists.|
|Lower level access roads (such as Admirall Helfrichsingel)||Bike lane||Speeds too high to safely be in mixed traffic||The volume on these roads didn’t seem to be high|
|Higher level access roads(such as Sir Winston Churchillaan)||Cycle track||Vertical separation necessary. Extremely unsafe to be with multiple lanes of fast moving traffic||This fast moving road has two 2-way cycle tracks on either side. Great connectivity between the neighborhoods|
The neighborhoods were very quiet and the speeds overall were very low. In my observations, I was quite impressed with how successful all the neighborhoods were at keeping the speeds low and the streets safe. I frequently saw children playing in the streets without a worry in their mind.
Overall, the bicycle use seemed lowest in Presidentenbuurt. This neighborhood seemed the most American(wide, untreated roads, more reliance on signage). Also, of all the Rijswijk neighborhoods, Presnidentenbuurt has the lowest Dutch population(see Fig 2), which could be a significant factor in why the bicycle usage is low. It could be a large factor in why the 30 km/h zone is not self-enforcing as the other seven neighborhoods are, due to a lack of urgency from residents and officials.
Figure 2—Chart showing demographic breakdown of Presidentenbuurt neighborhood
The other neighborhoods averaged around 15% “Westerner” population.
The Rijswijk areas surveyed were very densely populated. In the neighborhoods there is an average of 44 dwellings per hectare. The zoning of Rijswijk establishes more multi-family developments than single-family in the area, however, each neighborhood varies in which type of population(s) it serves.
United States comparison
Many United States’ neighborhoods prioritize cars. As a result, roads are wide and do not have speed control devices and pavement treatment. Many local roads are used as cut throughs, as well. This causes cars to drive faster, which, in turn, presents a safety hazard for residents.
Most of the Rijswijk neighborhoods(excluding Strijp and Eikelenburg, which are VINEX developments) were developed before 30 km/h zones became a treatment. This has required city officials and road designers to retrofit the roads to become self-enforcing 30km/h zones. Pavement was replaced with brick, entry treatments were made raised, speed control devices were implemented, and cut-throughs were eliminated in neighborhoods that were not originally designed to be 30 km/h. These retrofitting projects were incredibly successful at turning around the feel and safety of a neighborhood. If Rijswijk was able to retrofit local roads, why can’t US neighborhoods? The answer is they can! By constructing raised crossings and intersections, changing pavement to brick, inserting speed humps and chicanes, and eliminating through traffic routes, United States neighborhoods can be retrofitted to become safe, self-enforcing slow zones. This change is necessary to really make significant progress towards zero road deaths.
Centennial, CO has a neighborhood named “The Farm” that would be a perfect candidate for becoming a 30 km/h zone. As highlighted in the “CO-NL comparison” map, the roads in this neighborhood are very wide and paved in all flat black pavement. The current speed limit is 30 mph, but cars rarely go that speed. There is no design that causes speed limits to be self-enforcing, nor is there any design that is forgiving and mitigates driver mistakes(as a raised intersection would by physically slowing down a car that broke too late, for example). Cut through traffic is very common as well, which increase average daily traffic as well as average speed of cars. It would be ideal to have only origin/destination traffic driving on these neighborhood roads. By introducing measures that address the 3 main factors that make 30 km/h zones successful(entry treatments, speed control within the zones, and elimination of through traffic), a neighborhood such as “The Farm” can become a much safer, more livable, more child friendly area(which is especially important since there is a large elementary school within the neighborhood).
Municipalities establish 30 km/h zones with the goal of maximizing safety and livability of neighborhoods by lowering traffic volume and speeds. Overall, the 30 km/h zones in this section of Rijswijk were obviously effective. In my time observing, traffic volume was sufficiently low and traffic speed was incredibly safe. This was the case almost across the board. There were only a few instances where I thought a car was traveling too fast. I was quite impressed with all neighborhoods, except maybe Presidentenbuurt which stood out from the crowd. This neighborhood did seem to have lower bicycle usage and faster driving speeds, likely due to the lack of measures taken to make the 30 km/h zone self-enforcing and effective. Presidentenbuurt seemed very American-style. It reminded me a lot of “The Farm” in Centennial, CO. Besides retrofitting this neighborhood to make it like the rest, the only other improvement that came to mind was adding “T” junctions at entrances to slow traffic even further when entering. This could be a good additional entry treatment.
All effective road designs within these neighborhoods are premised on several principles of systematic safety, such as speed control and separation, predictability and recognizability, forgiveness, and functional harmony. The table below summarizes how the Rijswijk road designs are sustainably safe, based on the concepts core principles.
|Speed control and separation||
||Limit speed. Separate vulnerable road users from cars(especially fast moving ones) to avoid collisions||Must be self-enforcing to be effective|
|Predictability and recognizability||
||Make driver aware of intended use by repeating key design details on similar roads.||In the Netherlands, brick= slow. Access road always has a raised crossing when intersecting a local road.|
||Mitigate driver mistakes||Devices such as raised intersections will catch driver error if they happen to not slow down enough while approaching an intersection. A STOP sign does not do this.|
||Get cut through traffic out of neighborhoods||There is not one cut-through through a 30 km/h zone here that would save a driver time vs. using the access roads.|
ARTIESTENBUURT, RIJSWIJK | WEETMEER BUURTINFORMATIE
Your Bibliography: ”Artiestenbuurt, Rijswijk | Weetmeer Buurtinformatie”, Weetmeer.nl, 2017. [Online]. Available: http://www.weetmeer.nl/buurt/Rijswijk/Artiestenbuurt/06030443. [Accessed: 29- Jul- 2017].
DESTRIJP.NET – INTRODUCTIE
Your Bibliography: ”DeStrijp.net – Introductie”, Destrijp.net, 2017. [Online]. Available: http://www.destrijp.net/site/index.php?section=4. [Accessed: 29- Jul- 2017].
ZONES 30: URBAN RESIDENTIAL AREAS
Your Bibliography: ”Zones 30: urban residential areas”, SWOV Fact Sheet, 2017. [Online]. Available: https://www.swov.nl/sites/default/files/publicaties/gearchiveerde-factsheet/uk/fs_residential_areas_archived.pdf. [Accessed: 29- Jul- 2017].