1 Introduction
2 Stated choice experiment
2.1 Description of the choice situation
2.2 Design of stated choice experiment
car | FFCS | bus | taxi | SAV | |
---|---|---|---|---|---|
Travel costs [in Euro] | 1.2; 2.4; 3.6 | 1.2; 2.4; 3.6 | 1.2; 2.4; 3.6 | 3.6; 4.2; 4.8 | 2.4; 3.6; 4.8 |
Parking costs in Euro] | 0; 2.5; 5 | N.A. | N.A. | N.A. | N.A. |
Access and Egress Time [in min] | 2; 4; 6 | 6; 10; 14 | 2; 6; 10 | N.A. | N.A. |
Waiting Time [in min] | N.A. | N.A. | 1; 4; 7 | 1; 4; 7 | 1; 4; 7 |
In-Vehicle Time [in min] | 15; 20; 25 | 15, 20, 25 | 20; 25; 30 | 15; 20; 25 | 15; 20; 25 |
Parking search Time [in min] | 1; 4; 7 | 1; 4; 7 | N.A. | N.A. | N.A. |
3 Results
3.1 Respondent panel and sample composition
Characteristic | Total number (percent) [class] |
---|---|
Respondents: | 796 |
Mean age (standard deviation): | 41.78 (14.1) |
Respondents per age classes (in percent) [class]: | 204 (25.6%) [18–29]; 168 (21.1%) [30–39]; 153 (19.1%) [40–49]; 159 (20.0%) [50–59]; 112 (14.1%) [60–80] |
Gender: male; female (in percent): | 399 (50. 1%); 397 (49.9%) |
Driving license holder (in percent): | 684 (85.9%) |
Household with children (in percent): | 215 (27.1%) |
Household has access to at least one vehicle; and more than one vehicle (in percent): | 598 (75.1%); 168 (21.1%) |
Highest level of education (in percent) [class]: | 108 (13.6%) [Primary school and lower education]; 317 (39.8%) [High school or mid-level education]; 370 (46.5%) [higher education] |
Yearly household income (in percent) [class]: | 191 (24.0%) [0–30,000 Euro]; 321 (40.3%) [30,000–60,000 Euro]; 150 (18.8%) [more than 60,000 Euro]; 134 (16.8%) not reported |
Households with at least one household member subscribed to a car-sharing service in general and to a free-floating car-sharing service in particular (in percent): | 76 (9.1%) [Car-Sharing in general]; 24 (3.1%) [Free-Floating Car-Sharing] |
Uber user and/or chauffeur (in percent): | 97 (12.2%) |
3.2 Mode choice model estimation
3.2.1 Introducing nested logit models to account for shared unobserved attributes
3.2.2 Introducing latent classes to account for decision rule heterogeneity
3.2.3 Estimated parameters values
Class (class-membership probability in %) | Class 1 (62.9 %): “Brisk Sharers” | Class 2 (20.26 %): “Public Transport Enthusiasts” | Class 3 (16.79 %): “Car Captives” | ||||
---|---|---|---|---|---|---|---|
Utility Coefficients value [p-value]: *** = significant at 99% CI, ** = significant at 95% CI, * = significant at 90% CI N.A.: not applicable, constrained by specification | |||||||
ASCFFCS | 1.09 | [0.00]*** | 1.18 | [0.00]*** | -2.85 | [0.00]*** | |
ASCPT | 0.816 | [0.00]*** | 1.61 | [0.00]*** | -2.71 | [0.00]*** | |
ASCSAV | 1.30 | [0.00]*** | 1.22 | [0.00]*** | -2.92 | [0.00]*** | |
ASCtaxi | 1.21 | [0.00]*** | 1.23 | [0.00]*** | -2.63 | [0.00]*** | |
βcost_parking | -0.272 | [0.00]*** | -0.278 | [0.00]*** | -0.127 | [0.06]* | |
βcost | -0.218 | [0.00]*** | -0.147 | [0.03]** | -0.010 | [0.40] | |
βwalk | -0.02 | [0.00]*** | N.A. | -- | N.A. | -- | |
βwait | -0.028 | [0.00]*** | N.A. | -- | N.A. | -- | |
βIVT,FFCS | -0.025 | [0.00]*** | -0.005 | [0.09]* | -0.02 | [0.41] | |
βIVT,SAV | -0.025 | [0.00]*** | |||||
βIVT,taxi | -0.031 | [0.00]*** | |||||
βIVT,bus | -0.012 | [0.00]*** | |||||
βIVT,parkingSearch | -0.011 | [0.01]** | -0.068 | [0.00]*** | N.A. | -- | |
Class Membership value [p-value]: *** = significant at 99% CI, ** = significant at 95% CI, * = significant at 90% CI | |||||||
intercept δ | 0.00 | (fixed) | -0.69 | [0.00]*** | -1.68 | [0.00]*** | |
18 to 39 years old | 0.00 | (fixed) | -1.28 | [0.00]*** | -0.992 | [0.00]*** | |
high education | 0.00 | (fixed) | 0.11 | [0.63] | -0.517 | [0.03]** | |
currently private car for commuting | 0.00 | (fixed) | -1.79 | [0.00]*** | 1.77 | [0.00]*** | |
currently public transport for commuting | 0.00 | (fixed) | 1.09 | [0.00]*** | -0.65 | [0.23] | |
Nest Coefficients scale parameter [p-value]: *** = significant at 99% CI, ** = significant at 95% CI, * = significant at 90% CI | |||||||
μ1 | 1.00 | (fixed) | 1.00 | (fixed) | 1.00 | (fixed) | |
μ2 | 3.91 | [0.00]*** | 6.90 | [0.04]** | 4.55 | [0.37] |
- “Brisk Sharers” (class 1): This majority group (57%) prefers shared modes over private cars, as indicated by the strong and positive alternative specific constants (ASC) for all shared modes. Brisk Sharers show a much stronger sensitivity towards an increase in travel time than Public Transport Enthusiasts (class 2). Brisk Sharers have a higher likelihood to be younger than 40 years old. This age group consists mainly of the generational cohort known as the “millennials” or “generation Y” (born in the 1980s -1990s), who tend to be less car-oriented than previous generations and be more open towards new means of transportations [2, 15].
- “Public Transport Enthusiasts” (class 2): This group is the second largest group (20.3%) and represents individuals who currently tend to commute by public transport, and not by private car. They are more price-sensitive and much less sensitive to changes in in-vehicle-time than Brisk Sharers, but show an equally strong preference for shared modes in contrast to the private car. Public Transport Enthusiasts have a higher likelihood to be older than 40 years old.
- “Car Captives” (class 3): This small group (16.8%) consists of individuals who currently commute by private car. This group shows a strong preference towards the private car in the choice experiment as well, as indicated by the strong negative ASC for all shared modes. Car Captives are non-traders who can be characterized as mode-captives favouring private cars. In terms of their socio-economic profile, they tend to be older and less educated than the sample average.
3.2.4 Mode preferences
3.3 Model application: modal migration analysis
car | FFCS | bus | taxi | SAV | |
---|---|---|---|---|---|
Travel cost [in Euro] | 2.4 | 2.4 | 2.4 | 3.6 | 3.6 |
Parking cost [in Euro] | 0 | N.A. | N.A. | N.A. | N.A. |
Access/Egress time [in minutes] | 6 | 6 | 6 | N.A. | N.A. |
Waiting time [in minutes] | N.A. | N.A. | 4 | 4 | 4 |
In-vehicle-time [in minutes] | 20 | 20 | 20 | 20 | 20 |
Parking-search time [in minutes] | 1 | 1 | N.A. | N.A. | N.A. |
↓ | ↓ | ↓ | ↓ | ↓ | |
Estimated Choice Probability | 24% | 21% | 25% | 14% | 16% |
4 Discussion and conclusion
4.1 Preferences for shared (automated) modes
-
Car commuters are open for using shared mobility services providing a similar experience to their current mode, but they are not charmed by vehicle automation The findings of the migration analysis suggest that commuters who currently mainly use a private car show a high preference for FFCS. The migration to FFCS from this group can be further amplified when charging parking fees (which are not included in the simulated scenario), considering that the class of Car Captives shows a strong aversion towards parking costs.Commuters taking the car show a lower preference for the other modes of shared mobility included in the choice experiment. This group perceives the utility of SAV marginally lower than the utility of taxi, indicating this group does not see vehicle automation to be an added value in itself. Car Captives have been found before to be less likely to switch to SAV [19].
-
Commuters currently combining car and public transport are the most enthusiastic about shared (automated) mobility services Commuters currently opting for a combination of car and public transport for their commute are the most enthusiastic about FFCS and SAV. This group shows the strongest preference towards these modes and also shows the strongest difference in the perceived utility between car and FFCS, and the second-strongest difference in the perceived utility between taxi and SAV. This indicates that the added value of the new shared (automated) mobility service is the strongest for this group. A possible reason for this could be that this group has mobility needs that are neither met by a car or public transport services alone, and that FFCS and SAV are perceived to close this gap by combining the advantages of a car and public transport services.
-
Public transport users are the least impressed with on-demand shared (automated) mobility services For commuters currently using public transport, the introduction of shared automated vehicles increases the perceived utility for on-demand door-to-door services, as for this group a higher probability for choosing SAV than for choosing taxi has been estimated. However, no other group has lower mode choice probabilities for FFCS and SAV than this group. The latent class analysis shows that Public Transport Enthusiasts have a higher probability to feature older respondents and respondents having a lower level of education, and captures those that are more cost-averse rather than time-loss-averse. This group of people has been found before to be less likely to opt for automated vehicles [17].
-
Young and time-sensitive commuters are the most appreciative of vehicle automation The class of participants showing the greatest enthusiasm for FFCS and SAV are captured in the class of the Brisk Sharers (63% of the sample), who also show a strong preference for travelling in SAV over taxi. This class is characterised by being younger and more educated than the sample average.
-
Commuters currently cycling or walking see an added-value in vehicle automation The group of commuters currently walking or cycling to work shows the strongest difference in the perception of SAV and taxi. It should be noted that the mode choice experiment did not incorporate active mode options and thus forced this group to select exclusively between motorized modes. The estimated model therefore merely captures the difference in mode perceptions between the included modes, and not the perceived utility in relation to the modes this group is currently using.The findings in this study largely corroborate the image of the “early adopters” of shared (automated) vehicles sketched in previous studies, as summarized in the introduction. The main difference is that in this study neither gender nor the number of children significantly improved the clustering of the observed choices. Instead, the current mode choice showed to be a more reliable predictor for the collected sample. Different from Krueger et al. [25], the public transport users included in our study showed the lowest preference for SAV. In fact, survey respondents who combine public transport use and private car for their commuting trips showed the highest preference for SAV, as well as for FFCS. Indeed, our study showed that multi-modal commuters and those using active modes (walking or biking) have the highest preference for the new modes. Therefore we suggest adding these characteristics to the image of an “early adopter” of shared (automated) mobility services.