1.The pollution will become more and more serious ifthe number of cars and trucks gets larger and larger.
2.i didn't notice_ the traffic signal just now and ran thered light.
3. Careless_ riding caused his injury.
4. Motorcycle riders without helmets will get a fine whenriding.
5. Don't worry about her. She is in safety.

1. Both drivers and pedestrians should pay attention tothe traffic on the road.
2.Look out . The truck's coming! Get out of the way.
3.You should never use the elevator(电梯)in case ofa fire accident.
4. lf you are not careful on the road, you may be in danger
5. In a word , to stay safe is the most important thingto us all.

Discuss
What do people use bicycles for?
They use them for work, for sport or just for fun.What bicycle sports do you know about?
Bicycle road races, BMX...