Simulation-Based Connected and Automated Vehicle Models on Highway Sections: A Literature Review

Table 2

Simulation-based intelligent-vehicle studies: analyzed vehicle types, evaluation criteria, and main results.

Ref #	Analyzed vehicle types	Evaluation criteria	Main results
[32]	Manual vehicle,; ACC, CACC	Throughput	Throughput of the manual, ACC, and CACC vehicles were, respectively,; 2,050, 2,200, and 4,550 vehicles/h.
[29]	Manual vehicle,; ACC	Fuel consumptions and environmental effect (CO, HC, CO2, NOx)	The smooth response of the ACC vehicles has a beneficial effect on the environment.; These benefits vary with the levels of the disturbance, the position of the ACC vehicle in the string of manually driven vehicles and the ACC vehicle penetration.
[31]	Manual vehicle,; ACC	Throughput	A small proportion (5%) of ACC vehicles can improve the traffic flow.; An increasing proportion of ACC vehicles reduces traffic congestion.
[14]	Manual vehicle,; ACC	Throughput	ACC vehicles improve the traffic stability and the road capacity.; 25% of ACC eliminates traffic congestion during simulation (the cumulated travel time without ACC vehicles is 4,000 hours, but with 25% ACC vehicles 2,500 hours).
[30]	Manual vehicle,; ACC	Throughput	1% more ACC vehicles will lead to an increase in the road capacities by about 0.3%.
[18]	Manual vehicle, CAV, AV	Throughput	Increasing CAVs will have significant implications on the road capacity of highways.; Road capacity efficiency will be dependent on the level of automation.; The lane capacity increases from 2,046 to 6,450 vehicles/hour/lane with CAVs increases from 0% to 100%.
[19]	Manual vehicle,; AV	Throughput	AVs could considerably improve traffic flow.; The lane-changing frequency between neighboring lanes evolves with traffic density.; AV lane changing seems to be much less pronounced than that of the AV car-following.
[46]	Manual vehicle,; CAV	Average speed dispersion, travel time, space mean speed	Increasing percentage of AVs will reduce the total travel time and smooth traffic oscillations.
[45]	Manual vehicle, connected vehicle, AVs	Stability and throughput	CAVs can improve string stability, and automation is more effective in preventing shockwave formation and propagation.; Substantial throughput increases under certain penetration scenarios.
[44]	Manual vehicle,; CAV	Fuel consumption, travel time, throughput	CAVs can contribute to significant fuel consumption and travel time reduction.; CAVs allow for more stable traffic patterns even for high density traffic.
[15]	Manual vehicle,; CAV	Speed, vehicle position profile	Effectiveness of the CACC in absorbing certain disturbance and oscillation of speeds.; Speed oscillation decreases as vehicle position in the string increases.; Perfect communication/radar contributes string stability.
	Manual vehicle,; CACC	Throughput	A low-to-moderate penetration rate of CACC, the CACC impact is not statistically significant (advantages observed with a 40% or more CACC).; A very large improvement is noticed at a high penetration rate of CACC, especially in high traffic conditions.
[52]	Manual vehicle,; HDV with ACC, CACC functions	Fuel consumption; Space mean speed	The increasing HDV platooning in traffic flow results in more dramatic improvements on traffic efficiency.; Deceleration of the first HDV to a low speed during platoon formation will increase the formation time to a large extent in medium and heavy traffic.
[17]	Manual vehicle, AV	Average density; Average travel time; Average travel speed	The average density of autobahn segment remarkably improved (8.09%) during p.m. peak hours in the AV scenario.; The average travel speed enhanced relatively by 8.48%.; The average travel time improved by 9.00% in the AV scenario.
[37]	Manual vehicle, CACC	Throughput	Freeway capacity is 90% higher in a 100% CACC penetration compared to 0%.; The capacity increase is insignificant under low to medium CACC market-penetrations (e.g., 20–60%) in the absence of additional management strategies.
[36]	Manual vehicle, CACC	Bottleneck capacity	The freeway capacity increases quadratically as the CACC increases, with a maximum of 3080 vehicles/hour/lane at 100% CACC penetration.; The disturbance from the on-ramp traffic can reduce the freeway capacity by up to 13% but the bottleneck capacity still increases in as CACC increase.; There is very little gain in merge bottleneck capacity as CACC penetration increases from 0% to 20% when the on-ramp demand is high.; A rapid increase in bottleneck capacity from 80% to 100% CACC penetration, especially with high on-ramp inputs.
[56]	Manual vehicle, CACC	Throughput	The congestion reduction is higher when the market-penetration rate of the CACC-equipped vehicle increases. At a low penetration rate, the effect of the CACC on traffic dynamics is not significant.
[27]	Manual vehicle, ACC, CACC, and Here-I-Am (HIA) vehicle	Highway throughput	The use of ACC was unlikely to change lane capacity significantly.; The CACC can increase capacity greatly after its market-penetration reached moderate to high percentages (4000 vehicles/hour if all are the CACC or vehicle awareness device-VAD equipped).; The capacity benefits of CACC can be accelerated at somewhat lower market-penetrations, if the rest of the vehicles are equipped with VADs.
[21]	Manual vehicle, CACC	Throughput	The CACC can improve traffic-flow characteristics.; A low market-penetration rate of the CACC (< 40%) would not have an impact on the throughput.
[58]	Four ACC and; CACC experimental vehicles	Speed, distance gap, time gap	The IDM controller in the experimental test vehicles does not perceptibly follow the speed changes of the preceding vehicle.; Strings of consecutive ACC vehicles are unstable, amplifying the speed variations of preceding vehicles.; Strings of the consecutive CACC vehicles overcome these limitations, providing smooth and stable car following responses.
[59]	Manual vehicle; Non-platooned AVs; Platooned AVs	Fuel consumption; Emissions (HC, CO, NOx)	The AHS has much lower average fuel consumption operating under congested conditions, because of its smoother traffic flow, but slightly lower average fuel consumption at free-flow.; The AHS operating at 60 mph has substantially lower emissions per vehicle-mile traveled than non-automated traffic at the same average speed.; Vehicles that platoon in an AHS can expect additional 5 - 15% fuel savings and emission reduction due to the aerodynamic drafting effect.
[60]	Manual vehicle,; Heavy commercial vehicle-HGV,; AVs	Average travel speed	An increase of travel speed and decrease of average stop delay with the increase of percentage of the AVs.; Increases in estimated crash number at roundabouts when the AVs percentage is increased in terms of rear-end conflict.
[61]	Manual vehicle; CAV	Conflicts based on the threshold values of TTC (1.5 seconds) and PET (5 seconds).	The CAVs bring about compelling benefit to road safety as traffic conflicts significantly reduce even at relatively low market-penetration rates; (12–47%, 50–80%, 82–92% and 90–94% for 25%, 50%, 75% and 100% CAV penetration rates respectively).