Example of link impedance calculation
Table 92 to Table 95 show an example in which link impedance consists of the current travel time and road toll. For HGV transport systems which have a higher "value of time" the influence of road tolls on link impedance is less than for car transport systems.
Link length |
10,000 m |
Permitted maximum speed v0 car |
130 km/h |
Permitted maximum speed v0 HGV |
100 km/h |
Road toll for cars |
€1 |
Road toll for HGV |
€5 |
Capacity |
3,000 car units/h |
Car volume |
1,000 cars/h = 1,000 car units/h |
HGV volume |
100 HGV/h = 200 car units/h |
Value of time VOTCar |
18 €/h = 0.005 €/s |
Value of time VOTHGV |
36 €/h = 0.010 €/s |
VD function according to BPR |
with a = 1, b = 2, c = 1 |
Car travel time in unloaded network |
t0 car = 10 000 • 3.6 / 130 = 277s |
Car travel time in loaded network |
tCur car = 277 • (1+(1 200/3 000)²) = 321s |
Car speed in loaded network |
vCur car = 10 000 • 3.6 / 321 = 112 km/h |
HGV travel time in unloaded network |
t0 HGV = 10 000 • 3.6 / 100 = 360s |
HGV travel time in loaded network |
tCur HGV = MAX (321s; 360s) = 360s |
HGV speed in loaded network |
vCur HGV = 100 km/h |
HGV speed only declines if the volume is more than 1644 car units/h if: tCur = 277 • (1+(1644/3000)²) = 360s |
Car impedance in loaded network |
Rcar = 1 + 0.005 • 321 = 2.61 € |
HGV impedance in loaded network |
RHGV = 5 + 0.010 • 360 = 8.60 € |