PRE-DRIVE C2X Deliverable D0.3 Final report_20100929.pdf

Final Report PRE-DRIVE C2X 29.9.2010
Changes in driver behaviour through the use of C2X-applications can prevent traffic
breakdown at highway bottlenecks as well as increase traffic safety considerably.
Simulations of the effect of C2X-applications on traffic flow made with the above
mentioned simulation model show that C2X-applications can significantly improve
traffic flow characteristics. The use of a stochastic microscopic three-phase traffic
flow model in the United Network Model ensured high quality simulation results.
This is because the model can show and predict all known empirical spatiotemporal
features of traffic breakdown and resulting traffic patterns found in measured traffic
at highway bottlenecks
Traffic breakdown at an on-ramp bottleneck that causes the formation of complex
congested traffic pattern can be prevented through the use of vehicle
communication. This can occur when communicating vehicles send Decentralized
Floating Car Data messages about speed decrease in a neighbourhood of the
bottleneck and vehicles moving on the main road upstream receive the messages
increase time headways to make the merging of vehicles from on-ramp lane onto
the main road easier. At greater flow rates upstream of the bottleneck, when traffic
breakdown cannot be prevented nevertheless, the reduction in traffic congestion
that leads to the decrease in travel time and increase in traffic safety can be
achieved through the use of Decentralized Floating Car Data as well. This can occur
when communicating vehicles send a message about synchronized flow emergence
at the bottleneck and vehicles moving on the main road upstream received the
message increase time headways to each other.
A broken down vehicle in the right lane of a two-lane road can lead to traffic
breakdown at the breakdown location even if the flow rate is not great. Through the
sending of a danger warning message “broken down vehicle ahead”, vehicles
upstream are advised to change to the left lane earlier. This lane changing prevents
the traffic breakdown. The results are shown in Figure 47.
Figure 47: Effects of “broken down vehicle warning” on traffic flow
Results of the Friendly User Test
As discussed in chapter 2.2.5 a “Friendly User Test” has been conducted with 30
test persons. The subjects (15 female / 15 male) showed high interest in C2X
communication technology, which was the reason for them to participate in the user
test. Most of them knew the actual situation with RDS/TMC information available to
Deliverable D0.3 Version 1.0 61
Final Report