Floating road makes flooded areas passable

When the Netherlands' major rivers-the Ijssel, the Rhine, and the Meuse-overtop their banks, the flood-waters sometimes block roadways, causing access problems for local residents. Similar problems result when one of the country's many bridges is closed for repair. In search of an innovative solution, the Directorate-General for Public Works and Water Management recently held a design competition to solicit ideas for a floating road.

The winning team developed a system of aluminum modules, each 5.5 m wide, 3.5 m long, and 1.5 m high, that can be linked together to form a floating road for either temporary or permanent use. The team recently built and tested a prototype on a tributary of the Mouse in the Netherlands near Hedel.

While various types of floating bridges that can be rapidly assembled have been designed for military applications, driving on these structures is typically "so uncomfortable that they are useless" for civilians, says Jan Brouwer. The goal of the Dutch project, in contrast, was to create a floating road on which motorists could drive as safely and comfortably as on a normal road, at speeds of up to 80 km/h.

The modules are stiff, lightweight aluminum boxes that are partially filled with polystyrene to keep them afloat. The bottom of the structure is porous, allowing water to enter the modules and fill the spaces beneath and between the polystyrene blocks. This design imparts stability to the structure, says Frans Soetens, a structural engineer for TNO Building and Construction Research. The road is further stabilized by aluminum breakwaters on each side.

The modules are designed to be transported easily by truck. Once at the site, they are placed in the water and linked by stainless steel clamps. Some of the modules, which are spaced at regular intervals, are equipped with rings that project from the sides. Steel piles are driven through these rings to anchor the structure to the riverbed. The distance between the piles and the depth to which they are driven depend on local conditions. Constructing a road some 50 m long in this manner would typically take as little as two days, says Martin Cornelissen, the project designer for the DHV Group.

The 70 m long prototype, installed earlier this year, includes more than a dozen floating modules and two transitional structures, each 10m long, which form ramps on each bank of the river. It was tested for both a 2,000 kg private car and an emergency vehicle weighing 7,500 kg. Waves were also generated in the water to test the roads stability. The tests were successful, and the structure has now been approved for public use.

Silence is golden

Today's sound barriers are visually attractive and environmentally friendly

Many studies have shown that where vehicle noise is significant the construction of traffic noise harriers (sound walls) has been the most effective mechanism to curb vehicle noise for residents living next to high density roadways.

Noise barriers can be designed in one of two ways, to blend into the environment, or to make a dominant visual statement. Both can work well in different situations. A barrier can be blended into an area by using light and transparent materials. This allows natural light to pass through, and in many cases reduces the perceived height of the barrier.

In other situations a well designed barrier with strength of form and a firm, distinctive silhouette may help to strengthen the area. Earlier noise barriers are often ‘unsightly’. Today, they are well designed and blend well with the background.

As noise barriers arc often viewed at speed, heir appearance needs to be simple, because small decorations are likely to blur and appear cluttered when viewed at speed. However, it must also be taken into account that local The sound tube in Melbourne, Australia,

residents will also have designed to reduce roadway noise without

to view these barriers detracting from the area's aesthetics.

everyday,often for extended periods of time.

Excessive detailing of the barrier can increase the dominance of the barrier. Some experts believe it is generally more desirable to use colour, texture and landscaping in the overall design to help the barrier reflect the character of its surroundings.

The colour of noise barriers is an important aesthetic element. Generally colours are either chosen to help the barrier blend in to the environment, or to create a pleasing visual effect. Plantings at the base of noise barriers can improve the aesthetics of the barrier, as well as giving it a more natural feel.

The angle of noise barriers also affects their aesthetics. A barrier with a vertical profile can make people feel confined. Angling the wall can reduce this effect. However, deciding which way to angle the wall can also be difficult. Angling it away from the road gives drivers an increased feeling of space, but may make an increased feeling of confinement for those on the other side and visa-versa.

Noise barriers often appear incongruous or characterless; this is often a result, of poor design related to cost reduction. Although their main function should be to control traffic noise, the visual effect should not damage the surrounding areas.

To prevent noise from becoming a burden and haying detrimental consequences, Degussa AG's Business Unit Rohm Plexiglas has for many years been developing transparent noise control products and systems that are ideal both from an economical and ecological point of view. Examples can be found the world over. Today, transparent noise barriers made from Plexiglas Soundstop belong to the streetscape in many European countries, but also in Hong Kong, Japan and Australia.

Soundstop can be installed both flat and in the form of barrel vaults. By reflecting sound at the barrier made of Soundstop, the volume of noise in the area behind it is considerably reduced. Being transparent, the material offers a clear view from both sides.

The light-transmitting sheets also make an important contribution to road safety. Since they cast no harsh shadows on the road surface, drivers have no need to adjust to a constant change in lighting conditions, and remain in visual contact with their surroundings.

The weather resistance of Plexiglas means that the high light transmission and all other properties remain practically unchanged for many years.

Soundstop is offered in seven standard colours. Special colours can be developed on request. Moreover, the simple and inexpensive processing options it offers, such as thermoforming, cutting to size and drilling or surface treatment, leave virtually unlimited scope for individual designs.

The barrier can be installed using a simple post and foundation design. Weighing only 34 kg per m² no heavy lifting equipment is needed to install. It is available in heights up to 8.5m and in virtually any colour.