Impacts of automated passenger cars on the capacity of a freeway basic section: applicability in the determination of vehicle adjustment factors in mixed traffic

Sia M. Lyimo; Valerian Kwigizile; Jun-Seok Oh; Zachary D. Asher; Sia M. Lyimo; Valerian Kwigizile; Jun-Seok Oh; Zachary D. Asher

doi:10.48130/DTS-2023-0025

Figures (5) Tables (7)

Figure 1.
Comparison of speed-flow diagram between human-driven passenger cars and APCs.
Figure 2.
Passenger car equivalent (E_AV) at the various percent of APC penetration rates.
Figure 3.
Calculated adjustment (f_AV) factors at various percentages of APCs.
Figure 4.
Impacts of the percentage of HDHV and APCs on f_observed.
Figure 5.
Equivalent adjustment factors from the three approaches.

Scenario #	Description
1	Passenger's cars only (100% HDPCs + 0% HDHVs)
2	5% mixed traffic (95% HDPCs + 5% HDHVs)
3	10% mixed traffic (90% HDPCs + 10% HDHVs)
4	15% mixed traffic (85% HDPCs + 15% HDHVs)
5	20% mixed traffic (80% HDPCs + 20% HDHVs)
6	30% mixed traffic (70% HDPCs + 30% HDHVs)

Table 1.

Main simulation scenario for the human-driven traffic flow.

Parameters designation	Description	Default	APCs
CCO	Standstill distance (ft)	4.92	3.98
CC1	Following variation (s)	0.9	0.6
CC2	Following variation (m)	13.12	0
CC3	Threshold for entering following (s)	−8	−6
CC4	Negative following threshold (s)	−0.35	−0.1
CC5	Positive following threshold (s)	0.35	0.1
CC6	Speed dependency of oscillation (rad/s)	11.4	0
CC7	Oscillation acceleration (ft/s2)	0.82	0.33
CC8	Standstill acceleration (ft/s2)	11.48	13.12
CC9	Acceleration at 50 mph (ft/s2)	4.92	6.56

Table 2.

Driving behavior parameters for APCs modeling.

Percent of APCs	Difference in PCE	t	p > \|t\|	95% Conf. Interval
10 vs 0	−0.208	−22.230	<0.001*	−0.237	−0.180
20 vs 0	−0.220	−23.420	<0.001*	−0.248	−0.191
30 vs 0	−0.226	−24.090	<0.001*	−0.255	−0.197
40 vs 0	−0.228	−24.320	<0.001*	−0.257	−0.199
50 vs 0	−0.234	−24.920	<0.001*	−0.263	−0.205
60 vs 0	−0.228	−24.360	<0.001*	−0.257	−0.200
70 vs 0	−0.226	−24.120	<0.001*	−0.255	−0.197
20 vs 10	−0.011	−1.180	0.935	−0.040	0.018
30 vs 10	−0.017	−1.860	0.580	−0.046	0.011
40 vs 10	−0.020	−2.080	0.430	−0.048	0.009
50 vs 10	−0.025	−2.690	0.133	−0.054	0.004
60 vs 10	−0.020	−2.130	0.402	−0.049	0.009
70 vs 10	−0.018	−1.890	0.557	−0.047	0.011
30 vs 20	−0.006	−0.680	0.998	−0.035	0.022
40 vs 20	−0.008	−0.900	0.986	−0.037	0.020
50 vs 20	−0.014	−1.510	0.802	−0.043	0.015
60 vs 20	−0.009	−0.940	0.981	−0.038	0.020
70 vs 20	−0.007	−0.710	0.997	−0.035	0.022
40 vs 30	−0.002	−0.220	1.000	−0.031	0.027
50 vs 30	−0.008	−0.830	0.991	−0.037	0.021
60 vs 30	−0.003	−0.270	1.000	−0.031	0.026
70 vs 30	0.000	−0.030	1.000	−0.029	0.029
50 vs 40	−0.006	−0.610	0.999	−0.035	0.023
60 vs 40	0.000	−0.040	1.000	−0.029	0.028
70 vs 40	0.002	0.190	1.000	−0.027	0.031
60 vs 50	0.005	0.570	0.999	−0.024	0.034
70 vs 50	0.007	0.800	0.993	−0.021	0.036
70 vs 60	0.002	0.230	1.000	−0.027	0.031
The standard error remained constant (Std. Err = 0.009) for each experiment.

Table 3.

Comparison of E_AV for APCs at different MPRs.

Percent of APCs	Difference	p > \|t\|	[95% Conf. Interval]
10 vs 0	0.02	0.00	0.02	0.03
20 vs 0	0.05	0.00	0.04	0.06
30 vs 0	0.08	0.00	0.07	0.09
40 vs 0	0.12	0.00	0.11	0.12
50 vs 0	0.15	0.00	0.14	0.16
60 vs 0	0.19	0.00	0.18	0.19
70 vs 0	0.23	0.00	0.22	0.24
20 vs 10	0.03	0.00	0.02	0.03
30 vs 10	0.06	0.00	0.05	0.06
40 vs 10	0.09	0.00	0.09	0.10
50 vs 10	0.13	0.00	0.12	0.13
60 vs 10	0.16	0.00	0.16	0.17
70 vs 10	0.21	0.00	0.20	0.21
30 vs 20	0.03	0.00	0.02	0.04
40 vs 20	0.07	0.00	0.06	0.07
50 vs 20	0.10	0.00	0.09	0.11
60 vs 20	0.14	0.00	0.13	0.14
70 vs 20	0.18	0.00	0.17	0.19
40 vs 30	0.04	0.00	0.03	0.04
50 vs 30	0.07	0.00	0.06	0.08
60 vs 30	0.11	0.00	0.10	0.11
70 vs 30	0.15	0.00	0.14	0.16
50 vs 40	0.03	0.00	0.03	0.04
60 vs 40	0.07	0.00	0.07	0.08
70 vs 40	0.11	0.00	0.11	0.12
60 vs 50	0.04	0.00	0.03	0.04
70 vs 50	0.08	0.00	0.07	0.09
70 vs 60	0.04	0.00	0.04	0.05

Table 4.

Difference in adjustment factors for APCs at different MPRs.

Percent of APCs	Truck percentages	Difference in CAF	Std. Err.	p > \|t\|	[95% Conf. Interval]
0	5 vs 0	−0.08	0.00	0.00*	−0.09	−0.07
	10 vs 0	−0.13	0.00	0.00*	−0.14	−0.12
	15 vs 0	−0.16	0.00	0.00*	−0.17	−0.15
	20 vs 0	−0.19	0.00	0.00*	−0.20	−0.19
	30 vs 0	−0.25	0.00	0.00*	−0.26	−0.24
	10 vs 5	−0.05	0.00	0.00*	−0.06	−0.04
	15 vs 5	−0.08	0.00	0.00*	−0.09	−0.07
	20 vs 5	−0.11	0.00	0.00*	−0.12	−0.10
	30 vs 5	−0.17	0.00	0.00*	−0.17	−0.16
	15 vs 10	−0.03	0.00	0.00*	−0.04	−0.03
	20 vs 10	−0.07	0.00	0.00*	−0.07	−0.06
	30 vs 10	−0.12	0.00	0.00*	−0.13	−0.11
	20 vs 15	−0.03	0.00	0.00*	−0.04	−0.02
	30 vs 15	−0.09	0.00	0.00*	−0.09	−0.08
	30 vs 20	−0.05	0.00	0.00*	−0.06	−0.05
70	5 vs 0	−0.08	0.01	0.00*	−0.09	−0.06
	10 vs 0	−0.12	0.01	0.00*	−0.14	−0.11
	15 vs 0	−0.16	0.01	0.00*	−0.17	−0.14
	20 vs 0	−0.20	0.01	0.00*	−0.21	−0.18
	30 vs 0	−0.27	0.01	0.00*	−0.28	−0.25
	10 vs 5	−0.05	0.01	0.00*	−0.06	−0.03
	15 vs 5	−0.08	0.01	0.00*	−0.09	−0.06
	20 vs 5	−0.12	0.01	0.00*	−0.14	−0.10
	30 vs 5	−0.19	0.01	0.00*	−0.20	−0.17
	15 vs 10	−0.03	0.01	0.00*	−0.05	−0.02
	20 vs 10	−0.08	0.01	0.00*	−0.09	−0.06
	30 vs 10	−0.14	0.01	0.00*	−0.16	−0.13
	20 vs 15	−0.04	0.01	0.00*	−0.06	−0.03
	30 vs 15	−0.11	0.01	0.00*	−0.13	−0.10
	30 vs 20	−0.07	0.01	0.00*	−0.08	−0.05

Table 5.

Significant differences in f_observed at different percentages of APCs and HDHVs.

HDHV percentage	Percent of APCs	Observed adjustment factor (f_observed)	Calculated adjustment factor (f_HCM)	Std. Err.	p > \|t\|	[95% Conf. Interval]
5	0	0.919	0.919	0.00	1.00	−0.005	0.005
	10	0.940	0.941	0.49	0.63	−0.003	0.005
	20	0.962	0.965	1.40	0.17*	−0.001	0.007
	30	0.987	0.993	2.73	0.01*	0.002	0.010
	40	1.015	1.026	4.02	0.00*	0.005	0.016
	50	1.045	1.058	4.13	0.00*	0.006	0.019
	60	1.076	1.093	6.55	0.00*	0.012	0.023
	70	1.111	1.131	4.88	0.00*	0.011	0.028
10	0	0.871	0.871	0.00	1.00	−0.005	0.005
	10	0.898	0.901	0.95	0.35	−0.003	0.008
	20	0.920	0.926	2.26	0.03*	0.001	0.011
	30	0.944	0.956	5.58	0.00*	0.008	0.016
	40	0.974	0.990	5.74	0.00*	0.010	0.022
	50	1.004	1.026	6.09	0.00*	0.015	0.029
	60	1.035	1.064	7.57	0.00*	0.021	0.037
	70	1.066	1.104	8.31	0.00*	0.028	0.047
15	0	0.838	0.838	0.00	1.00	−0.006	0.006
	10	0.862	0.868	2.60	0.01*	0.001	0.011
	20	0.885	0.894	3.41	0.00*	0.003	0.014
	30	0.912	0.928	6.08	0.00*	0.011	0.021
	40	0.938	0.960	7.63	0.00*	0.016	0.027
	50	0.967	0.998	10.32	0.00*	0.025	0.037
	60	0.996	1.036	11.14	0.00*	0.032	0.047
	70	1.033	1.081	9.77	0.00*	0.038	0.059
20	0	0.806	0.806	0.00	1.00	−0.007	0.007
	10	0.828	0.833	2.03	0.05*	0.000	0.011
	20	0.853	0.865	5.95	0.00*	0.008	0.017
	30	0.876	0.896	6.04	0.00*	0.013	0.027
	40	0.902	0.929	7.27	0.00*	0.020	0.035
	50	0.932	0.969	9.36	0.00*	0.029	0.044
	60	0.960	1.009	10.53	0.00*	0.039	0.058
	70	0.991	1.050	8.09	0.00*	0.044	0.073
30	0	0.752	0.752	0.00	1.00	−0.007	0.007
	10	0.773	0.781	2.51	0.02*	0.002	0.014
	20	0.795	0.809	4.17	0.00*	0.007	0.021
	30	0.816	0.839	5.72	0.00*	0.015	0.031
	40	0.843	0.875	8.27	0.00*	0.025	0.040
	50	0.866	0.910	9.48	0.00*	0.035	0.053
	60	0.894	0.955	8.30	0.00*	0.046	0.075
	70	0.922	0.996	9.16	0.00*	0.058	0.090

Table 6.

Differences in adjustment factors between the observed (f_observed) and calculated (f_HCM).

Truck percentage	Percent of APCs	Observed adjustment factor (f_observed)	Calculated adjustment factor (f_proposed)	Std. Err.	p > \|t\|	[95% Conf. Interval]
5	0	0.919	0.919	0.00	1.00	−0.005	0.005
	10	0.940	0.940	0.00	1.00	−0.004	0.004
	20	0.962	0.962	0.00	1.00	−0.004	0.004
	30	0.987	0.987	0.00	1.00	−0.005	0.005
	40	1.015	1.015	0.00	1.00	−0.005	0.005
	50	1.045	1.045	0.00	1.00	−0.006	0.006
	60	1.076	1.076	0.00	1.00	−0.006	0.006
	70	1.111	1.111	0.00	1.00	−0.008	0.008
10	0	0.871	0.871	0.00	1.00	−0.005	0.005
	10	0.898	0.898	0.00	1.00	−0.006	0.006
	20	0.920	0.920	0.00	1.00	−0.005	0.005
	30	0.944	0.944	0.00	1.00	−0.004	0.004
	40	0.974	0.974	0.00	1.00	−0.006	0.006
	50	1.004	1.004	0.00	1.00	−0.007	0.007
	60	1.035	1.035	0.00	1.00	−0.008	0.008
	70	1.066	1.066	0.00	1.00	−0.009	0.009
15	0	0.838	0.838	0.00	1.00	−0.006	0.006
	10	0.862	0.862	0.00	1.00	−0.005	0.005
	20	0.885	0.885	0.00	1.00	−0.005	0.005
	30	0.912	0.912	0.00	1.00	−0.005	0.005
	40	0.938	0.938	0.00	1.00	−0.006	0.006
	50	0.967	0.967	0.00	1.00	−0.006	0.006
	60	0.996	0.996	0.00	1.00	−0.008	0.008
	70	1.033	1.033	0.00	1.00	−0.010	0.010
20	0	0.806	0.806	0.00	1.00	−0.007	0.007
	10	0.828	0.828	0.00	1.00	−0.006	0.006
	20	0.853	0.853	0.00	1.00	−0.005	0.005
	30	0.876	0.876	0.00	1.00	−0.006	0.006
	40	0.902	0.902	0.00	1.00	−0.007	0.007
	50	0.932	0.932	0.00	1.00	−0.008	0.008
	60	0.960	0.960	0.00	1.00	−0.010	0.010
	70	0.991	0.991	0.01	1.00	−0.014	0.014
30	0	0.752	0.752	0.00	1.00	−0.007	0.007
	10	0.773	0.773	0.00	1.00	−0.006	0.006
	20	0.795	0.795	0.00	1.00	−0.007	0.007
	30	0.816	0.816	0.00	1.00	−0.008	0.008
	40	0.843	0.843	0.00	1.00	−0.008	0.008
	50	0.866	0.866	0.00	1.00	−0.009	0.009
	60	0.894	0.894	0.01	1.00	−0.013	0.013
	70	0.922	0.922	0.01	1.00	−0.015	0.015

Table 7.

Differences in adjustment factors between the observed (f_observed) and calculated (f_proposed).