The average travel speed can be calculated using the traffic flow and traffic density. These fundamental characteristics of a traffic flow are linked by the following formula:
\[ \text{flow} = \text{speed} \times \text{density} \]
To calculate the average travel speed, rearrange the formula to:
\[ \text{speed} = \frac{\text{flow}}{\text{density}} \]
Assume a traffic flow of 600 vehicles/hour and a density of 10 vehicles/km:
\[ \text{speed} = \frac{600 \, \text{vehicles/hour}}{10 \, \text{vehicles/km}} = 60 \, \text{km/h} \]
Thus, the average travel speed is 60 km/h.