Colons instead of dashes

Colons can be used to replace dashes ( - ). These are common in informal writing; however, they are not appropriate in academic texts. Notice in the following sentence

The manager's incoming brief contained one major task - to organise and allocate team roles more efficiently.

the dash could be replaced with a colon

The manager's incoming brief contained one major task : to organise and allocate team roles more efficiently.

This dash in this sentence

These factors have been identified as important contributory factors to the large increase of repetitive strain injury during the 1980s - new technology, changing work practices and inappropriate medical management.

could also be replaced with a colon

These factors have been identified as important contributory factors to the large increase of repetitive strain injury during the 1980s : new technology, changing work practices and inappropriate medical management.

In both sentences above, the role of the colon is to signal that an explanation is to follow.

BEWARE: NOT ALL DASHES CAN BE REPLACED WITH COLONS
Occasionally, you will find that informal sentences punctuated with dashes will require the dashes to be replaced with commas rather than colons; for example, the sentence

Angry truck-drivers from across the state - who were all protesting against excessive petrol prices - organised blockades of many petroleum supply depots.

in an academic context should be written as:

Angry truck-drivers from across the state, who were all protesting against excessive petrol prices, organised blockades of many petroleum supply depots.