Traffic Assignment exercise using User Equilibrium (UE) method
Overview
A simple traffic assignment exercise for learning fundamentals of User Equilibrium method
Traffic Assignment (the fourth step of four step modeling)
In this assignemt you will practice and learn about the fundamentals of User Equilibrium traffic assignment in the field of urban transportation and land use modeling. Please note that the network presented in this practice is a simple network consisiting of two nodes and two possible pathes between them. In the real world cases, obviously the network is much more complex and you need to use appropriate software packages and computers to perform a sound traffic assignment model.
As discussed, assume the following network consisting of two zones and two possible pathes between them exists in a hypothetical urban area. assuming a user equilibrium condition and a total flow of 3100 vehicles per hour, calculate the followings:
- travel time on each route
- traffic volumes on each route
- total system travel time
Traffic Assignment (the fourth step of four step modeling)-Solution
According to the data, the total flow in the network is 3100 vehicles. Thus, we have x1+x2=3.1
- step 1: first we need to check the usability of each road. we do this step to ensure that if all the flow is assigned to one path, that path should not have still the lower travel time:
all to path 1:
T1(3.1)=17.8min
T2(0)=11min
all to path 2:
T1(0)=8.5min
T2(3.1)=30.22min
- Step 2: given that the question require to apply a user equilibrium method, then t1 should be equal to t2 and also we have x2=3.1-x1
8.5+3x1=11+2x22
by pluging in the values and calculating the equasion, x1=1.86 and x2=1.24
- Step 3: now we have to calculate the updated travel times t1=t2=14.08
Now the total system travel time is:
Z(x)=X1T1(X1)+X2T2(X2)=1860+veh/hr(14.08min)+1240 veh/hr(14.08min)=727.46 veh/hr