Table 2.
Linear mixed effect model estimates of the effect of adaptive cruise control engagement and other covariates on fuel consumption across six predefined situations
| Dependent variable: Fuel Consumption | ||||||
|---|---|---|---|---|---|---|
| (1) | (2) | (3) | (4) | (5) | (6) | |
| Cruise | Brake, Stop & Accelerate | Brake & Accelerate | Accelerate | Brake | Creep | |
| Inverse Avg Speed (km/h)−1 | 5.594*** | 2.956*** | 2.035*** | 4.082*** | 3.406*** | 2.931*** |
| (0.152) | (0.121) | (0.190) | (0.216) | (0.125) | (0.127) | |
| [<2e−16] | [<2e−16] | [9.27e−15] | [<2e−16] | [<2e−16] | [<2e−16] | |
| ACC Engagement | 0.142*** | − 0.316*** | −0.278*** | −0.714*** | 0.334*** | −1.175 |
| (0.017) | (0.060) | (0.026) | (0.089) | (0.037) | (1.599) | |
| [<2e−16] | [1.21e−07] | [<2e−16] | [8.28e−16] | [<2e−16] | [0.4629] | |
| Inverse Trip Distance (1/km) | 0.314*** | 2.880*** | 2.459*** | 2.777*** | − 0.179*** | 0.460** |
| (0.003) | (0.014) | (0.007) | (0.018) | (0.008) | (0.189) | |
| [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | [0.0152] | |
| Starting Vehicle Speed (km/h) | −0.129*** | −0.137*** | −0.117*** | 0.533*** | −1.401*** | −0.161** |
| (0.001) | (0.001) | (0.001) | (0.040) | (0.052) | (0.065) | |
| [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | [0.0136] | |
| Ending Vehicle Speed (km/h) | 0.151*** | 0.248*** | 0.234*** | − 1.519*** | 0.588*** | 0.081 |
| (0.001) | (0.001) | (0.001) | (0.084) | (0.015) | (0.062) | |
| [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | [0.1898] | |
| Min Vehicle Speed (km/h) | −0.059*** | 0.072 | −0.114*** | −0.739*** | −0.567*** | |
| (0.002) | (0.274) | (0.0005) | (0.040) | (0.015) | ||
| [<2e−16] | [0.7916] | [<2e−16] | [<2e−16] | [<2e−16] | ||
| Max Vehicle Speed (km/h) | 0.127*** | 0.125*** | 0.084*** | 1.891*** | 1.381*** | 0.007 |
| (0.002) | (0.002) | (0.001) | (0.083) | (0.052) | (0.110) | |
| [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | [0.9463] | |
| Trip Elevation Change | 0.037*** | 0.300*** | 0.240*** | 0.370*** | 0.264*** | 0.196** |
| (0.0003) | (0.003) | (0.001) | (0.004) | (0.002) | (0.085) | |
| [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | [0.0212] | |
| Avg. Ambient Temperature | − 0.009*** | 0.093*** | 0.022*** | 0.036*** | 0.009*** | 0.333*** |
| (0.001) | (0.002) | (0.001) | (0.003) | (0.001) | (0.039) | |
| [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | [1.14e−09] | [<2e−16] | |
| Avg. Engine Temperature | − 0.050*** | − 0.123*** | − 0.084*** | − 0.108*** | − 0.028*** | − 0.353*** |
| (0.0005) | (0.001) | (0.001) | (0.001) | (0.001) | (0.036) | |
| [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | |
| Constant | 0.294* | −0.890** | 2.265*** | −5.405*** | 4.575*** | 37.389*** |
| (0.162) | (0.348) | (0.218) | (0.440) | (0.162) | (4.355) | |
| [0.0735] | [0.0118] | [<2e−16] | [<2e−16] | [<2e−16] | [<2e−16] | |
| Observations | 283,589 | 126,871 | 249,879 | 38,730 | 79,775 | 961 |
| Log Likelihood | −710,619.700 | −406,352.400 | −698,783.900 | −118,174.300 | −210,477.500 | −3,847.556 |
| Akaike Inf. Crit. | 1,421,271.000 | 812,736.700 | 1,397,600.000 | 236,380.600 | 420,986.900 | 7725.111 |
| Bayesian Inf. Crit. | 1,421,440.000 | 812,892.800 | 1,397,767.000 | 236,517.600 | 421,135.500 | 7798.131 |
Note: 7D3*p < 0.1, **p < 0.05, ***p < 0.01.
The main numbers in bold represent the estimated effects evaluated using t-tests based on Satterthwaite’s method; numbers in parentheses represent the standard errors, and included in brackets are two-sided based p-values.