A typical suspension bridge can be seen below. A suspension bridge is composed of a roadway (sometimes called a deck) suspended by steel cables. The four towers hold up the steel cables which in turn hold up the roadway.

This type of bridge is used where a wide gap / distanced is to be crossed and typical examples are the Golden Gate Suspension Bridge in San Francisco, the Akashi Kaikyo Suspension Bridge in Japan and the Humber Bridge in the UK. The Akashi Kaikyo suspension Bridge is over a distance of four miles in length and each tower is nearly as high as the Eiffel Tower (three hundred metres).

The steel cables are held in position by enormous concrete anchor blocks. These are at either end of the bridge. Each anchor block weighs more than the amount of cable it has to hold as well as a large proportion of the weight of the roadway. The anchor blocks must also be heavy enough to hold up the number of vehicles that are expected to be on the roadway at anytime.

The main steel cables are extremely thick. Each main cable is composed of smaller cables bound together to form an extremely strong single cable.

An example of the thickness/diameter of a main cable is seen opposite. The cables diameter equal to the height of the man.