Simulation of an On-Ramp
This szenario demonstrates, how an on-ramp acts as a stationary
bottleneck provoquing a traffic breakdown on the main road
UPSTREAM of the on-ramp and
FREE traffic downstream.
-
With the initial settings, upstream
propagating stop-and-go waves on the main road are triggered
at the on-ramp region!
The on-ramp acts as generator of the waves, but any other type of
flow-restricting inhomogeneity ("bottleneck") could do the same.
Now vary the traffic flows of the main road and the on-ramp.
-
At
an reduced inflow of 2000 veh./h, free traffic can be sustained
for up to 20 min but sooner or later breaks down.
- At 1600
veh./h, no breakdown occurs, but an existing jam will not
dissolve! This so-called hysteresis is the basis why
traffic-control
measures to
prevent the breakdown have a huge application potential.
-
On increasing the ramp flow to 800 veh./h, and decreasing the
main flow to 1600
veh./h, observe a stationary localized traffic breakdown "pinned" at the
ramp region. Only for higher inflows, the upstream front
will propagate further upstream giving rise to an extended congested region!
-
Play with the politeness factor and switching threshold
to change the aggressivity of the ramp vehicles.