How to use 30 km/h zones: Examples from the Czech Republic

Publikováno: 15. září. 2023, 14 min. čtení
Publikováno: 15. září. 2023, 14 min. čtení

The majority of roads in cities are service and residential streets where traffic calming measures are necessary. There is no reason for residential areas to have roads designed for speeds of 50 km/h or higher. Let’s consider several effective traffic calming measures, including non-structural ones, that can be implemented immediately without waiting for a complete street reconstruction and that can establish 30 km/h zones.

This article is a statement by the AutoMat Association.

The text was created as part of the Central European Active Mobility Lab (CEAML) project supported by the European Climate Foundation. The original text was published on June 8, 2023, on the AutoMat Association’s website.

Restricting speed is an ongoing trend

The speed of cars in urban areas is directly related to road safety, as well as traffic flow, street design with consideration for diverse groups of people and their needs, and the environment and residents‘ health. For at least the past fifty years, there has been a noticeable trend of reducing the maximum speed of vehicles in cities. In the 1960s, it was possible to drive at unlimited speed in Czechoslovak cities during the night (between 23:00 and 5:00), without any speed limit. During the day, a speed limit of 60 km/h applied in the 1970s and 1980s. In 1989, the nighttime exemption was abolished, and the maximum speed in urban areas was set at 60 km/h regardless of the time of day. This was further reduced to 50 km/h in 1997.

Today, there is further traffic calming in cities towards a speed limit of 30 km/h. This calming is no longer happening centrally through changes in the law but is being implemented independently by cities from the ground up, for various reasons that we have already summarized on this website. These reasons primarily include significantly increased safety for pedestrians and cyclists, improved traffic flow considering congestion and spacing between vehicles, and reduced noise and emissions from motorized traffic. Local authorities also approach speed reduction to enhance visibility triangles and increase the number of parking spaces at intersection edges.

How to do it?

In this text, we will look at specific ways to calm traffic when implementing 30 km/h zones. While it is possible to limit the maximum speed by placing a traffic sign, this signage should be complemented by additional calming elements to ensure that the actual vehicle speed does not exceed the local limit. If the street design, in terms of lane width and preference for car traffic, still resembles a road designed for higher speeds, the calming effect is likely to be limited. During reconstruction, it is possible to reshape the street or sections of the street in a way that corresponds to lower design speeds, and the street’s character will naturally lead to lower speeds of passing vehicles, even without a maximum speed restriction. Between simply lowering the maximum speed and reconstructing the street, there are other tools available to calm the street and achieve a functional solution without extensive construction.

Traffic signs

Traffic signage can limit the maximum speed in a specific section or in an entire area. Typically, this involves the placement of vertical traffic signs B20a (maximum allowed speed) or IZ8a (restricted traffic zone).

The effect of vertical traffic signs can be enhanced by combining them with horizontal traffic signs. This involves duplicating the same sign to reinforce the perception of a change in the speed limit on the driver’s side.

Construction solution

Traffic calming measures are desirable to be implemented during street reconstructions. Every street has a lifespan due to aging and wear of surfaces, as well as repairs and replacement of infrastructure. This lifespan is typically around 50 years. Current streets, before reconstruction, often reflect the design of the 1970s when different speed limits applied, and streets were primarily designed to maximize capacity for automobile traffic. Therefore, it is desirable that today’s reconstructions do not simply restore the previous state, which may be undesirable in terms of safety and usability for people. The following part of the text discusses the opportunity for effective traffic calming without waiting for a complete reconstruction. Now, let’s look at the newly renovated Gorký Street in Brno.

Gorkého Street underwent a complete reconstruction in 2019, which also resulted in traffic calming. The original „entrance“ to the street had very wide curves for car passage, a long pedestrian crossing, and minimalist corners. The maximum speed in this residential street was 50 km/h.

The original entrance to the street has been transformed into more of an entrance. The street corners have been extended into the space and fitted with protective bollards. When entering the street, drivers are informed about the change in the nature of the street and the speed limit not only by vertical traffic signs but also by other elements. The previous large turning curve has been replaced with a narrower entrance to the street. The entrance is designed as a raised roadway up to the level of the corner, and this section is paved with cobblestones instead of asphalt. This provides drivers with information about the change in the character of the street and the alteration of the road surface, with the transition over the raised threshold and the curve designed for lower speeds. The actual entrance to the street leads to a slowing down of the vehicle, and the driver receives feedback on the reduced speed through the surface and the narrowed and elevated entrance.

The enlargement of the corner space has been utilized not only to calm the entrance of cars but also to plant new trees and install bicycle racks. The new, shorter pedestrian crossing increases pedestrian safety, and the placement of bollards on the corners prevents illegal parking on the sidewalk, which could endanger the visibility of pedestrians when crossing the road.

The intersection of Gorkého Street with other streets was addressed similarly to the street entrance. The comparison of one of the intersections before and after reconstruction is visible in the photo above. Originally, the intersection was a large asphalt area, with sidewalks being pressed against the buildings to maximize the width of the intersection area. Under this arrangement, there was constant illegal parking within the intersection and its immediate vicinity, which reduced visibility, especially when crossing the intersection. Through the reconstruction, the corners were extended into the space, and the intersection area was reconfigured to meet the needs of automobile traffic. The corners are again protected against illegal parking by the installation of bollards. The surface in the intersection has been changed to cobblestones, and the intersection itself has been raised to the level of the sidewalks. Although there are no marked pedestrian crossings in the intersection, the design of the intersection allows pedestrians to cross comfortably and safely. Drivers entering the intersection instinctively slow down and share the space with pedestrians.

Gorkého Street serves as an example where calming is achieved through the spatial arrangement of the street. Although the maximum speed limit is formally set at 30 km/h, the calming effect and actual traffic behavior corresponding to this limit are primarily influenced by the new street design, which directly affects the drivers‘ behavior.

Calming using traffic devices and other elements

Merely reducing the maximum speed does not necessarily lead to calming traffic. Furthermore, it is not always necessary to wait for street reconstruction to effectively calm traffic. It is possible to implement effective calming measures using non-constructional elements such as traffic devices or curbs filled with paving stones. Below are several examples of how this approach can contribute to traffic calming.

The image above shows the entrance to a 30km/h zone with a significant calming effect. The vertical traffic sign is complemented by striking horizontal markings, which are further emphasized by a white frame. The driving lane is narrowed on the left side by a contraflow bike lane, which is separated from the driving lane by a double white longitudinal line. This doubling visually narrows the width of the driving lane and cognitively encourages drivers to slow down. The entrance to the 30km/h zone is further enhanced by a series of traffic bulges, which contribute to slowing down vehicles and reinforce the perception that the driver is entering a 30km/h zone. At the same time, cyclists are allowed to pass through the series of traffic bulges in both directions by omitting one button on each side at the edges.

An example of traffic calming measures that uses street closure combined with maintaining accessibility for pedestrians and cyclists can be found at the intersection of Strojnická and Veletržní streets in Prague. This intersection was calmed following the opening of the Blanka tunnel complex. The original design of the intersection dates back to the 1970s and consisted of two connecting three-lane roads.

The result of this action is the calming of Strojnická Street. In connection with the construction of new capacity for motor vehicles in the Blanka tunnel complex, the excess lane capacity on the surface was utilized for traffic calming. Instead of the original three lanes, two parking lanes, one driving lane, and one contraflow protected bike lane serving as a two-way cycle path were created. The continuity with Veletržní Street was visually closed off using traffic devices, city blocks, and granite cobblestones. At the same time, pedestrian access was maintained, and people can ride bicycles through the section in both directions. This action demonstrates that it is possible to effectively calm automobile traffic and create a functional 30km/h zone without making structural changes to the street.

Another example of non-structural intervention is the use of foldable guiding curbs filled with paving stones, also known as „lego.“ Lego can be used where it is suitable and desirable to redistribute space between different functions. Typically, it involves transforming oversized lanes from the previous century into lanes with widths that correspond to current standards and design speeds. In other words, it is not appropriate to have lanes in the city with a width of, for example, 4 meters, designed for a speed of 130 km/h when the maximum permitted speed in that area is 30 km/h. For a speed of 30 km/h, a lane width of 3.25 meters is sufficient in the case of public transport, and 3 meters or less is sufficient for other traffic. Lego can also be used in intersection modifications, which are located in the city but have the nature of an exit from a high-speed road.

Conclusion

While the debate about reducing speed limits to 30 km/h in cities is still ongoing in the Czech Republic, the process of traffic calming is already underway. We don’t have to look only to foreign examples for inspiration; there are also noteworthy examples to follow in Czech cities. It is evident that simply installing a vertical traffic sign to lower the maximum allowed speed to 30 km/h does not lead to the desired results. For effective traffic calming, it is necessary to have a cognitive impact on drivers and bring about a change in their behavior. This can be achieved through both street infrastructure modifications and non-structural changes in the operational and spatial layout using traffic devices and other elements described in this text.

This is an adjusted ChatGPT translation of this article: https://mestemnakole.cz/2023/06/jak-na-zony-30-priklady-z-ceska/

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