This study measured the impacts of autonomous intelligent cruise control (AICC) systems on freeway capacities in the Netherlands. Ten (10) different Intelligent Cruise Control (ICC) designs were investigated and then evaluated based on market penetration (10 percent, 20 percent, 50 percent, and 100 percent), and driver behavior (headway). Microscopic simulation techniques (FOSIM and MIXIC) were used to evaluate AICC and its impact on freeway capacity during bottleneck conditions. In the Netherlands, a typical headway value of 1.2 seconds was used to represent driver behavior at max capacity. In addition, headway values of 0.8, 1.0, and 1.4 seconds were input to account for headway variations.

The freeway geometry used in the model consisted of an on-ramp (250 meters in length) attached to a two-lane freeway (5000 meter in length). Capacity detectors were mounted 1 kilometer (km) downstream from of the on-ramp. Upstream detectors were used to maintain appropriate congestion levels for each simulation. During each 2.5 hour simulation, traffic demand was increased from the beginning to the end of each scenario. It took approximately one hour to generate the upstream congestion necessary to estimate downstream discharge at full capacity. The capacity estimates were based on data collected during the last 5-minute period of each scenario. The baseline model results of 4285 vehicles per hour (vph) were comparable to actual motorway data collected in the Netherlands.

The following five AICC designs were evaluated based on different headway time parameters and different levels of AICC technology market penetration.

Nominal AICC design: Expected to be the first generation AICC in the Netherlands this model simulated assisted braking with limited assisted braking deceleration of (–3 m/s2) (meters per second every second) over a limited operational speed range of 30 to 150 kilometers per hour (km/h). This design also required manual reactivation after driver over-ride.

Extended AICC design: Same as normal design, but with automatic reactivation of the assisted braking system.

All speed AICC design: Same as extended design, but with support at all speeds (0 to 150km/h).

Queue AICC design: Same as extended design, but support only at stop and go speeds (0 to 60 km/h).

Complete AICC design: Full braking capabilities (deceleration of (-5 m/s2), support at all speeds, and automatic re-activation of assisted braking system.

RESULTS

In general, the conference paper reported the following results:

100% MARKET PENETRATION

0.8 Second Headway Settings:

• The Complete AICC design generated capacity gains of approximately 12.4 percent.
• The Extended AICC design generated capacity gains of approximately 7 percent.

1.0 Second Headway Settings:

• The Extended AICC design generated capacity gains of approximately 1.1 percent.
• The Normal AICC design generated capacity gains of approximately 4.0 percent.

1.2 Second Headway Settings:

• The Complete AICC design generated capacity gains of approximately 0.6 percent.
• The Extended AICC design generated capacity gains of approximately 1.5 percent.
• The Normal AICC design generated capacity gains of approximately 1.5 percent.
• The Queue AICC generated capacity losses of approxiamtely (-1.6) percent.
• The All-Speed AICC generated capacity losses of approxiamtely (-0.7) percent.

50% MARKET PENETRATION

0.8 Second Headway Settings:

• The Complete AICC design generated capacity gains of approximately 9.7 percent.
• The Extended AICC design generated capacity gains of approximately 3.4 percent.

1.0 Second Headway Settings:

• The Extended AICC design generated capacity gains of approximately 4.3 percent.
• The Normal AICC design generated capacity gains of approximately 4.0 percent.

1.2 Second Headway Settings:

• The Complete AICC design generated capacity gains of approximately 2.2 percent.
• The Extended AICC design generated capacity gains of approximately 1.0 percent.
• The Normal AICC esign generated capacity gains of approximately 1.5 percent.
• The Queue AICC generated capacity losses of approxiamtely (-1.0) percent.
• The All-Speed AICC generated capacity losses of approxiamtely 1.4 percent.

20% MARKET PENETRATION

0.8 Second Headway Settings:

• The Complete AICC design generated capacity gains of approximately 5.0 percent.
• The Extended AICC design generated capacity gains of approximately 3.2 percent.

1.0 Second Headway Settings:

• The Extended AICC design generated capacity gains of approximately 2.5 percent.
• The Normal AICC design generated capacity gains of approximately 2.0 percent.

1.2 Second Headway Settings:

• The Complete AICC design generated capacity gains of approximately 0.5 percent.
• The Extended AICC design generated capacity gains of approximately 1.0 percent.
• The Normal AICC generated capacity losses of approxiamtely (-0.9) percent.
• The Queue AICC design generated capacity gains of approximately 0.8 percent.
• The All-Speed AICC design generated capacity gains of approximately 0.5 percent.