On the two lane carriageways, roadworks restrict the width of both traffic lanes, generating a bottleneck to the traffic flow. The maximum flow per lane on the unobstructed carriageway is 2100 vehicles per hour whilst on the section under repairing the maximum flow per lane reduces to 1200 vehicles per hour. When stationary, vehicles are spaced at average distance headway of 6 m. It may be assumed that there is a linear relationship between speed and density. When the traffic flow approaching the roadworks is 3500 vehicles per hour, calculate:
1the speed of the traffic system a considerable distance in advance of the bottleneck;
2the speed of the traffic stream immediately before the commencement of the bottleneck; and
3the speed of the shockwave foamed by the bottleneck.