Written by Oliver Nowalski and Robert Meissner
Service roads, or called parallel roads in the CROW manual (p121, 127) are a unique way of dealing with the turbulence caused by local traffic interacting with through traffic on moderate to high speed roads.Turbulent traffic is one of the main causes of accidents in streets because of the difference in speed of cars in through traffic and local traffic. Service roads are designed to run parallel to main roads and give local traffic access to on-street parking, driveways, and shopping areas. The limited access allowed between a service road and the main throughway means that there are far fewer locations where traffic is merging onto the throughway.
In the Netherlands, engineers have utilized service roads to benefit cyclists as well as automobiles. Because service roads only carry local traffic, the speed on these roads is low (their speed limit is 30 km/h), making it an ideal environment for cyclists. Because the speed and volume is so low, no additional treatments are needed to make a service road a safe bike facility. As shown on the map above in green, bike paths lead to the service roads where the bikes can easily mix with local traffic, staying separate from the busy adjacent road. In the Netherlands, service roads are often linked together with bike paths to help create a comprehensive bicycle route, with the bike path links serving as barriers to through motor traffic. Since service roads serve a dual purpose, they are an inexpensive way to create routes in cycling network, compared to cycle tracks or stand-alone bike paths.
Service roads are not advantageous to cycling unless the traffic is light, and automobile speeds are low. Service roads are purposely constructed to be discontinuous sections of road, meaning that through traffic cannot use it to get from one main street to another. Since the only traffic on it will be cars accessing the houses or shops along the service road, traffic is substantially lower that on the main roads, and speeds are kept down due to the short segments of roadway. Also, service roads in Holland do not connect directly to a main perpendicular road. This prohibits traffic from getting directly onto the service road and using it as another thoughway. If service roads were to connect at perpendicular roads, that intersection would have 2 or 3 parallel roads crossing the street instead of 1. Having discontinuous service roads makes the intersection much simpler and safer.
The discontinuity that reduces automobile traffic does not apply for cyclists, which is what makes using service roads for cycling so convenient. Instead of the service road ending entirely, permeable barriers are installed so that bikes can continue on, while cars are forced to exit the service road. Bike paths or cycletracks link up to the service roads at these points, and a continuous bike network is created.
Below are some examples of where cycle tracks or bike paths meet service roads, and how they are made safe and easily identified by cyclists.
Service roads are very useful pieces of infrastructure, and the CROW manual helps to determine where and when these roads should be used. They also give design parameters for the construction of a service road. The table below helps to clarify is which situation a service road should be utilized.
Table 14 of the CROW manual states that cycle tracks or parallel roads are recommended for bicycles on district access roads (roads with 50km/h or faster automobile traffic) inside the built up area. The built up area typically has a high population density, so a service road can be used to benefit cars, bikes, and pedestrians at these locations. The houses and shops that need access to the main road use the service road as their neighborhood street where pedestrians and bikes are safe to move around freely, but they still have easy access to the main road when needed. If there is a neighborhood or shops along the district access road, a parallel road should be considered.
It is necessary to clarify that apart from being statistically safe, cyclists need to feel comfortable while riding their bikes. This means that even though cyclists may be relatively safe while riding mixed with cars in a 30 km/h service road, if the service road has a lot of automobile traffic or a lot of parking turbulence (commercial shopping), cyclists should get separate facilities, like a bike lane, or the street should have treatments that slow traffic, like chicanes or speed bumps.
Application of Service Roads
The previous example was just a typical outline of where a service road could be used. In fact, service roads can be used for many different applications in any kind of environment. Click the following link to learn about the varied types of service roads.
To find out how each type of service road can benefit the community and it's inhabitants, click the following link to learn about benefits of service roads.
US Example - Comm Ave vs. Winston Churchilllaan
The Netherlands have used their service roads to provide maximum benefits for all forms of transportation, while keeping their roads safe and un-congested. The US however, has taken a different approach, and their service roads only service the automobile. In areas where service roads are used along highways in the US, the roads are wide, straight, and conducive to high speeds. This is contrary to the Dutch system where traffic is slowed down to make the roads safe for bicycles. The design itself, not the speed limits, control traffic on Dutch roads, and this method works incredibly well. Paving in brick, speed bumps and raised crossings, narrow lanes, and chicanes all help to keep speed under control. Any number of these methods translates easily to American roads, and would have similar effects on traffic. Cyclists would feel more comfortable around slower traffic, and that is crucial to getting people onto their bikes.
An example of a service road in America that could operate well with Dutch techniques applied is Commonwealth Avenue in Boston, MA. Comm Ave is a four lane street with traffic in both directions, and service roads built on either side of the street.
The service roads provide on street parking for, and access to, all of the apartment buildings that line the street. The service roads are separated from Comm Ave on one side by the MBTA Green line trolley and on the other by a 6’ concrete median. In this densely populated area, cycling is an efficient way of getting around, but no bike facilities are marked in the service lanes. Most of the road is for parking, so there is very little fast moving traffic. A bike lane running on the left side of the service road, next to the parallel parked cars, would still leave room for auto traffic to drive next to cyclists. The lane width that the cars would lose would also reduce the speed of traffic because cars wouldn’t have as large a space to travel in. To further reduce the speed of auto traffic, speed bumps could be used as a method of traffic calming, and the road could be paved with brick. (Even though brick is a lot more expensive than asphalt, this would drastically reduce automobile speed in this street and make this residential area look a lot better). Comm Ave could also benefit from permeable barriers. The service roads are continuous along a long section of Comm Ave, and this promotes fast traffic. The picture below also illustrates how complicated an intersection becomes when service roads meet a main perpendicular road.
A near perfect roadway that Comm Ave can use as a model is located in the town of Riswijk. They also have four lanes of traffic, a light rail track, but just one service road. Riswijk used a one way service road, but allowed bicycle traffic to travel against the flow of traffic. Bicycles moving with the flow have a separate cycle track next to the parking area. This allows great bicycle facilities, while still having the means to reduce turbulent traffic on main streets.