People have needs to cross overtop of things that sometimes can only be met by the construction of a bridge.  These needs and the reasons for choosing to build a bridge are listed below.

Needs

People have many different needs for building a bridge.  Some of these include the need to:

- carry people or other living things;
- carry cars and trucks;
- carry trains; and
- carry utilities (cables, pipes, water),

over top of something.  

Reasons

The reasons for doing this include the need to:

- cross something (rivers, valleys, roads, railways) that is in the way for safety reasons (such as a pedestrian bridge overtop of a major road);
- cross something for performance reasons (such as Lethbridge's railway bridge); and/or
- cross something for convenience reasons (such as the +15 walkways that exist in Calgary, Alberta, Canada.).

Log Entry #1

You or your group needs to find out what the need and the reason for building the bridge were and record this in your research log under key question #1.