2. Put the questions to the answers:

1. Ancient Mesopotamia, Syria and Egypt.

2. By slow and crude methods of distillation.

3. 4000 to 5000 years ago in Iraq.

4. Along the Tigris river.

5. For waterproofing and mummification.

6. In 1595.

7. A short distance from the shore of the Gulf of Paria.

8. From Trinidad Lake.

9. It contains many impurities and foreign matter.

10. For paving purposes.

HOME – READING

Text 7 D

1. Mind some special terms to understand the text properly:

Girder bridge – балочний міст

Truss bridge – фермовий міст

Arch bridge – арковий міст

Cantilever bridge – консольний міст

Suspension bridge – висячий міст

Cable-stayed bridge – кабельний міст

Moveable bridge – рухомий міст

2. Read the text and match the type of the bridge with one of the features given below:

• A roadway that is moved entirely or partially.

• A roadway hanging from steel cables supported by two high towers.

• Spans in the form of arches.

• The cables that support the roadway are connected directly to the towers.

• Has two independent beams that extend from opposite banks of a waterway.

• Frameworks, arranged in the form of triangles.

• Beams’ ends simply rest on piers or abutments.

KINDS OF BRIDGES

There are seven main kinds of bridges: 1) girder bridges, 2) truss bridges, 3) arch bridges, 4) cantilever bridges, 5) suspension bridges, 6) cable-stayed bridges, 7) moveable bridges.

The types of bridges vary in total length, the length of their spans, and the weight they can support. Before deciding which kind to build at a particular place, engineers determine the length of the structure and of each span. They also must consider the maximum load that the bridge will carry and the materials available to construct the bridge.

Girder bridges, which include many highway bridges, are made of beams called girders whose ends simply rest on piers or abutments. These bridges may be used to cross most areas. The span length of girder bridges ranges up to 300 metres.

Truss bridges are supported by frameworks called trusses. The parts of the trusses are arranged in the form of triangles. Such bridges are built over canyons, rivers and other areas. A truss bridge may have a main span that extends more than 300 metres.

Arch bridges are structures in which each span forms an arch. The spans range up to about 518 metres long. The arch bridge is one of the oldest types of bridges. Early arch bridges consisted of large stone blocks wedged together to form an arch. Today, the majority of arch bridges that have short spans are made of concrete or wood. Arch bridges with long spans are built of concrete or steel.

Cantilever bridges consist of two independent beams called cantilevers that extend from opposite banks of a waterway. The two cantilevers are joined together above the middle of the waterway by a beam, girder or truss. Cantilever bridges may have spans as long as about 549 metres. Most bridges of the cantilever type are made of prestressed concrete.

Suspension bridges are perhaps the most impressive type of bridge because of their long main span and especially attractive appearance. These bridges have a roadway that hangs from steel cables that are supported by two high towers.

Suspension bridges are used to span great distances. Most suspension bridges have main span more than 300 metres, but some have a main span longer than 1200 metres. Suspension bridges are also used to cross deep water or steep canyons, and in other places where the construction of piers is especially difficult and expensive. These bridges require only two piers, each of which supports a tower. A suspension bridge may sway in a strong wind. To minimize such movement, most suspension bridges have a thick structure that supports the roadway. This type of structure helps stiffen the bridge and is called a stiffening girder.

Cable-stayed bridges resemble suspension bridges. Both have roadway that hang from cables, and both have towers. In a cable-stayed bridge, however, the cables that support the roadway are connected directly to the towers.

Moveable bridges have a roadway that is moved entirely or partially to provide enough clearance for large ships to pass.

ADDITIONAL READING

HOW ROADS AND HIGHWAYS ARE MAINTAINED

Repairing damage and resurfacing. Roads and highways gradually wear out. The work of repairing and resurfacing is called maintenance. Maintenance also includes removing ice and snow, painting stripes on pavement, cutting grass, putting up signs, and caring for roadside shoulders, roadsides and bridges.

Gravel and other similar type roads have to be smoothed quite often. Surfaces and edges of bituminous materials are repaired by patching with new material where worn spots develop from travel or because of weak spots in the ground underneath. Every 10-15 years many roads with bituminous surfaces are resurfaced completely.

Workers repair concrete pavements by digging out broken sections and putting in new concrete. They often repair cracks by filling them with asphalt. Many older concrete pavements must be resurfaced completely.

Clearing ice and snow. Most roads and highways must serve the year round. So they must be kept free from snow and ice in winter. Trucks with V-shaped or straight-blade plows attached to the front clear the roads when it snows. In deep drifts, special snowplows are needed. Some of the most powerful snowplows are called rotary plows. Rotary plows have a big screw at the front that chews into the snowdrifts and pulls the snow back into a large fan. The fan shoots the snow to one side of the road.

Often roads and highways that are slippery from ice and snow must have salt, chemicals or sand spread on them to keep them passable.

PEDESTRIANS, BEWARE!

Since the late 1970-s, more than 6,700 pedestrians have been killed annually by cars or other vehicles. That’s the equivalent of a Value-Jet crash every six days. According to the Surface Transportation Policy Project, you’re more likely to be killed by a stranger in a car than by a stranger with a gun.

Even the good news is grim. Pedestrian fatalities fell 14% in the ten years ending 1996, the latest year with complete statistics. But that’s still more than 6,000 deaths a year on average, and total pedestrian traffic is falling even faster. The National Personal Transportation Survey reports that discrete pedestrian journeys to the dry cleaners, to the office, etc. – fell from 7.7% of all trips in 1990 to 5.4% in 1995. This suggests the ratio of fatalities to trips actually is rising.

Many cities have achieved significant reductions in pedestrian deaths, often with such “traffic calming” designs as speed bumps and intersection circles. Seattle, which has installed more than 700 circles, cut fatalities by 18% between 1986 and 1995.

Such devices do slow speeding fire trucks, as well as speeding pickup trucks. But studies show the delay is barely a few seconds per obstacle, not enough to make a significant difference in response times.

And, of course, slower traffic means fewer calls for emergency crews.

Other strategies include better traffic enforcement and safety education programs for drivers and walkers.

Plainly, pedestrian cause some of their problems: alcohol, impatience and inattention are familiar contributors to accidents.

SUPERHIGHWAYS

Negotiating such highways as freeways, expressways or Interstates requires some adjustments in your driving habits. Because access is limited, it is important to plan exit points and service stops well in advance.

High speeds make it vital to look well ahead in order to spot potential hazards and to maintain a safe distance between you and a vehicle in front of you. Scan at least 12 seconds ahead. To check this distance, select a stationary object ahead and start counting: it should take you 12 seconds to arrive at that point. Keep a minimum of 3 or 4 seconds between you and a vehicle ahead; this will allow you time to adjust to other’s maneuvers. Check your distance by choosing a fixed object and counting seconds from the time the car ahead passes it until you do.

Entering and leaving a superhighway require special techniques. As you move down the ramp to enter the highway, check traffic with quick glances over your shoulder and in the outside mirror. Find a gap in the through lane, then time you approach to blend into that gap at traffic-flow speed. Do not stop unless there is no choice. You might have to adjust your speed in the acceleration lane to merge smoothly with other traffic. Always signal! When you leave a freeway, signal but do not slow down until you are completely in the deceleration lane. Then slow to the posted exit speed.

Listening comprehension