# Non-Compliant Behaviour of Automated Vehicles in a Mixed Traffic Environment
## 4 Experiment and Results
### Simulation Results

Table 6: Overview of mean simulation results considering all simulation runs for each scenario (S)  
Figure 9: Time headway distributions of scenarios A0, A3, and C3. in their acceleration phase and not yet driving at the desired speed. In addition, the speed distributions of scenarios A3 and C3 showed peaks at 80 km/h and 130 km/h, reflected by AVs being on the main carriageway. AVs did not exceed the maximum allowed speed (130 km/h for cars and 80 km/h for trucks) but tried to minimize travel time, which is why they drove at the maximum allowed speed in free-flow traffic situations. The higher the AV penetration rate, the higher the share of vehicles travelling at maximum allowed speed but the lower the amount of drivers driving too fast. Regarding lane-changing, the results of scenarios C3 and D3 are shown in Figures (a)a-c and (b)b,c. Both scenarios considered an AV penetration rate of 50% and the AVs had to keep a minimum time headway of 1.8 s. In scenario C3, non-compliant trajectories were prohibited, whereas AVs were allowed to reduce the time headway (\(\tau_{min,NC}\)) to 1.0 s for a maximum duration (\(T_{max,NC}\)) of 5 s in scenario D3. Figure 11: Lane change location distribution of scenarios C3 and D3. **(a)** C3: LC location of human drivers; **(b)** C3: 50% AV, NC prohibited LC location of AVs; **(c)** D3: 50% AV, NC permitted LC location of AVs. Figure 12: Gap acceptance distribution of scenarios C3 and D3. **(a)** C3: Gap acceptance human drivers; **(b)** C3: 50% AV, NC prohibited gap acceptance AVs; **(c)** D3: 50% AV, NC permitted gap acceptance AVs. Figure 10: Speed distributions of scenarios A0, A3, and C3. The focus lay on the mandatory merging lane changes performed by the human-driven and automated vehicles in the on-ramp area, which allowed a comparison between the Vissim internal lane-change model and the developed automated driving functions. Both free and congested traffic states were considered in the derived result data. First, we analyzed the lane change location indicated by the on-ramp position where a lane-change maneuver started. The histograms and cumulative distribution functions are shown in Figure 11a-c. The x-axis shows the lane change location, ranging from 0 to 250 m, which represents the position of the gore and the end of the acceleration lane, respectively. The gore is the location at which the merging area begins and vehicles are allowed to merge into the main road (see Figure 8). Figure 11a shows the distribution of the lane change location for all human-driven vehicles controlled by Vissim. It can be seen that more than 20% of all vehicles performed the lane change at the very beginning of the acceleration lane. In comparison, the results for AVs in Figure 11b showed that almost 10% of all AVs failed to perform a lane change before the end of the acceleration lane. These AVs most likely had to stop at the end of the acceleration lane, which is undesirable since stationary vehicles can be a safety risk and it is rather difficult for a stationary vehicle to find a suitable time gap in the target lane from a standstill. These situations can be prevented if AVs are allowed to execute non-compliant trajectories, which can be seen in Figure 11c. In this case, 18% of all AVs found a suitable gap in the target lane at the very beginning of the acceleration lane. Less than 5% did not manage to merge into the main carriageway, which is a substantial reduction compared with scenario C3. In addition, differences can be observed regarding the gap acceptance behavior in Figure 12a-c, which also explains the improved merging behavior of AVs when the non-compliant mode was permitted. The distribution in Figure 12a for human-driven vehicles shows a small peak at very low time headways. Further analysis revealed that these low headways usually occurred in situations when the lag vehicle in the target lane was a rather slow vehicle (e.g., a truck).