Distance-and-time graphs

We use distance-and-time graphs to show journeys. It is always very important that you read all the information shown on these type of graphs.

A graph showing one vehicle's journey

If we look at the graph shown below, you can see that the time in hours is along the horizontal, and the distance in miles is on the vertical axis. This graph represents a journey that Jan took, in travelling to Glasgow and back, from Cumbernauld.

Important points to note are:

• It took half an hour to travel a distance of miles
• Between 1pm and 3pm, there was no distance travelled. This means that the car had stopped.
• The journey back, after 3pm, took one hour.

A graph showing two different journeys in the same direction

The next graph shows two different journeys. You can see that there is a difference with the steepness of the lines drawn. Remember that, the steeper the line, the faster the average speed. We can calculate the average speeds, by reading distances from the graph, and dividing by the time taken.

Line A: How long does journey A last, and what distance is travelled?

The journey takes hours, and the distance travelled is km.

Line B : How long does journey B last, and what distance is travelled?

The journey takes hour, and the distance travelled is also km.

This means that the average speeds are:

A: km per hour

B: km per hour

You will also notice from the graph that the two lines cross. This means that, if the two vehicles were travelling along the same route, they would have met at that point, which was just after 10am. The vehicle on journey B overtook vehicle A.