阅读下面的短文，用方框中所给单词的适当形式填空，使文意通顺、正确。（每个单词限用一次）

Overhead bridges are found in many parts of Lanzhou, especially in places where traffic is heavy and crossing the road is very        .
The purpose of these overhead bridges is to enable passengers to cross road         . Overhead bridges are used in very much the same way as zebra crossings. They are more efficient     less convenient because people have toclimb up a long flight of steps. This is inconvenient especially to old people. When passengers are         a zebra crossing, traffic is held up. This is why the government has built many overhead bridges to help passengers and to keep traffic moving     the same time.
The government of Lanzhou has          lots of money in building these bridges. For their own safety, passengers         be encouraged to use them instead of risking their lives by running across the road. Old people, however, may find                  a little difficult climbing up and down the steps, but it is still         safer than walking across the road with all the dangerous of moving traffic.
Overhead bridges serve a very useful purpose. Passengers, both old and young, should make a        to use them. This will prevent unnecessary accidents and loss of life.