Platform competition with partial multihoming under differentiation: a note

A model of a two-sided market with two horizontally differentiated platforms and multihoming on one side is developed. In contrast to recent contributions, it is shown that platforms do not necessarily generate all revenues on the multihoming side by charging a higher price. Also, whether platforms' pricing structures favor exclusivity over multihoming is ambiguous.multihoming

Towards computational models for road-user interaction: Drivers overtaking pedestrians and cyclists

Introduction: Crashes resulting from a failed interaction between drivers and vulnerable road users, such as pedestrians or cyclists, can lead to severe injuries or fatalities, especially after failed overtaking maneuvers on rural roads where designated refuge areas are often absent, and impact speeds high. This thesis contains two studies that shed light on driver interaction with either 1) a pedestrian or 2) a cyclist, and oncoming traffic while overtaking. Methods: The first study modeled driver behavior in pedestrian-overtaking maneuvers from naturalistic and field test data, quantifying the effect of the pedestrian’s walking direction and position, as well as the presence of oncoming traffic, on the lateral passing distance and overtaking speed. The second study modeled cyclist-overtaking maneuvers with data from a test-track experiment to quantify how the factors time gap to the oncoming traffic and cyclist lane position affect safety metrics during the maneuver and the overtaking strategy (i.e., flying or accelerative, depending on whether the driver overtook before or after the oncoming traffic had passed, respectively). Results: The results showed that, while overtaking, drivers reduced their safety margins to a pedestrian when the pedestrian was walking against the traffic direction, closer to the lane and when oncoming traffic was present. Results for cyclist overtaking were similar, showing that drivers left smaller safety margins when the cyclist rode closer to the center of the lane or when the time gap to the oncoming traffic was shorter. Under these critical conditions, drivers were more likely to opt for an accelerative maneuver than a flying one. The oncoming traffic had the most influence on drivers’ behavior among all modeling factors, in both pedestrian- and cyclist-overtaking maneuvers. Conclusion: Drivers compromised the risk of a head-on collision with the oncoming traffic by increasing the risk of rear-ending or side-swiping the pedestrian or cyclist. This thesis has implications for infrastructure design, policymaking, car assessment programs, and specifically how vehicular active safety systems may benefit from the developed models to allow more timely and yet acceptable activations

The Impact of Market Characteristics on Price Setting and Market Outcomes: Four Essays

The thesis deals with the question how market characteristics and the change thereof affect market players� price-setting decisions and market outcomes. The market characteristics which are analyzed are the possibility to multihome, market transparency, differentiation, and inequity aversion. The first three models use the concept of horizontal product differentiation. The fourth model looks at bilateral bargaining in a double-auction framework with inequity-averse sellers and buyers. The first model on two-sided markets with one singlehoming and one multihoming side shows that due to product differentiation, platforms are no longer local monopolists on the multihoming side which benefits the latter as it may end up paying a lower price than the singlehoming side. The second model shows that with elastic demand, an increase in market transparency on the customer side may have a stabilizing effect for a collusive agreement: Depending on the degree of differentiation and on the level of transparency already achieved, a more transparent market may be bad news for customers as collusion may be facilitated. The third model looks at the implications of different internal decision-making structures for collusive stability. It is shown that when transportation costs are high, collusion is more stable under the delegation of decision-making powers. Furthermore, collusion with maximum prices is more profitable if price setting is delegated to the local units. The opposite is true for low discount factors. The fourth model shows that if compassion is sufficiently strong in a double-auction environment, an efficient equilibrium exists such that all gains of trade are realized. The opposite holds in a situation where compassion is weak and in the limit of infinitely strong envy as trade then breaks down completely. The analysis also shows that bids in a separating equilibrium are further away from (closer to) truth-telling, the greater the importance of envy (compassion). Moreover, pooling equilibria are shown to be always more inefficient compared to the case without inequity aversion

Drivers overtaking cyclists and pedestrians: Modeling road-user behavior for traffic safety

In a world aiming to shift to more sustainable modes of transportation, vulnerable road users (VRUs) like cyclists and pedestrians are still confronted with significant barriers to safety, particularly on rural roads where overtaking maneuvers represent a frequent and dangerous interaction with motorized traffic. If drivers misjudge their kinematics, even near-crashes without physical contact can harm the perceived safety of the VRU, which may decrease the willingness to continue cycling or walking on these roads. Crash risks when overtaking VRUs exist in different overtaking phases: when approaching the VRU, steering out, passing, and eventually returning. To make overtaking VRUs safer, improvements to policymaking, infrastructure, and vehicles are needed. However, these improvements need models that can describe or predict road-user behavior in overtaking, which was the objective of this thesis. Based on data sets obtained from a test-track experiment, field-test studies, and naturalistic studies, this thesis developed behavioral models for both objective and perceived safety of drivers and VRUs in different overtaking phases. The results indicate that drivers’ and VRUs’ behavior is mainly influenced by their highest crash or injury risk. The descriptive models showed that a close oncoming vehicle could reduce a driver’s safety margins to the VRU in all phases. Furthermore, the VRU behavior may affect the driver’s behavior; for instance, through lane positioning and, for pedestrians, walking direction. Infrastructure design and policymaking should focus on preventing overtaking in areas where oncoming vehicles are hard to estimate and enforcing sufficient clearances to the cyclist, stratified by speed. The predictive models can help vehicle safety systems adapt to drivers to become more acceptable, for instance, when assisting drivers in the decision to overtake or not. They may further help optimize road networks’ objective and perceived safety

Evaluation of bone allograft processing methods: Impact on decellularization efficacy, biocompatibility and mesenchymal stem cell functionality

The outcome of this study shows a higher efficacy in decellularization for sonication- based processed allografts (SPAs) over chemically processed allografts (CPAs) based on DNA quantification, histological and scanning electron microscopy (SEM) evaluation. Moreover, the decellularization efficacy of SPAs was comparable to two commercial grafts, Tutoplast® processed allografts (TPAs) and Bio-Oss® processed 44 xenografts (BPXs), used as additional reference, also in terms of commercially standardized products. Biocompatibility assessment based on extracts derived from decellularized grafts showed a decrease in mesenchymal stem cell (MSC) viability for SPAs and CPAs, as well as for the commercially available BPXs. In contrast, biocompatibility was not impaired for TPAs, which also showed a better performance after reseeding with MSCs as indicated by confocal laser scanning microscopy (CSLM) and DNA assessment in order to monitor cellular proliferation. Here, a significant increase in DNA throughout a two-week time frame could be shown. BPXs induced a tentative increase in alkaline phosphatase (ALP) activity and mineralization in MSCs potentially associated with the high calcium content. Even though SPAs extracts showed a noticeable reduction of in vitro biocompatibility, results after reseeding with MSCs were comparable to commercially available grafts used in this study. Nevertheless, in this present study, TPAs combined the best in vitro biocompatibility and performance in terms of proliferation and osteogenic differentiation after reseeding with MSCs

Modeling Drivers’ Strategy When Overtaking Cyclists in the Presence of Oncoming Traffic

Overtaking a cyclist on a two-lane rural road with oncoming traffic is a challenging task for any driver. Failing this task can lead to severe injuries or even death, because of the potentially high impact speed in a possible collision. To avoid a rear-end collision with the cyclist, drivers need to make a timely and accurate decision about whether to steer and overtake the cyclist, or brake and let the oncoming traffic pass first. If this decision is delayed, for instance because the driver is distracted, neither braking nor steering may eventually keep the driver from crashing—at that point, rear-ending a cyclist may be the safest alternative for the driver. Active safety systems such as forward collision warning that help drivers being alert and avoiding collisions may be enhanced with driver models to reduce activations perceived as false positive. In this study, we developed a driver model based on logistic regression using data from a test-track experiment. The model can predict the probability and confidence of drivers braking and steering while approaching a cyclist during an overtaking, and therefore this model may improve collision warning systems. In both an in-sample and out-of-sample evaluation, the model identified drivers’ intent to overtake with high accuracy (0.99 and 0.90, respectively). The model can be integrated into a warning system that leverages the deviance of the actual driver behavior from the behavior predicted by the model to allow timely warnings without compromising driver acceptance

Internal decision-making rules and collusion

We study the impact of internal decision-making structures on the stability of collusive agreements. To this end, we use a three-firm spatial competition model where two firms belong to the same holding company. The holding company can decide to set prices itself or to delegate this decision to its local units. It is shown that when transportation costs are high, collusion is more stable under delegation. Furthermore, collusion with maximum prices is more profitable if price setting is delegated to the local units. Profitability is reversed for low discount factors

A data-driven framework for the safe integration of micro-mobility into the transport system: Comparing bicycles and e-scooters in field trials

Introduction: Recent advances in technology create new opportunities for micro-mobility solutions even as they pose new challenges to transport safety. For instance, in the last few years, e-scooters have become increasingly popular in several cities worldwide; however, in many cases, the municipalities were simply unprepared for the new competition for urban space between traditional road users and e-scooters, so that bans became a necessary, albeit drastic, solution. In many countries, traditional vehicles (such as bicycles) may not be intrinsically safer than e-scooters but are considered less of a safety threat, possibly because—for cyclists—social norms, traffic regulations, and access to infrastructure are established, reducing the number of negative stakeholders. Understanding e-scooter kinematics and e-scooterist behavior may help resolve conflicts among road users, by favoring a data-driven integration of these new e-vehicles into the transport system. In fact, regulations and solutions supported by data are more likely to be acceptable and effective for all stakeholders. As new personal-mobility solutions enter the market, e-scooters may just be the beginning of a micro-mobility revolution. Method: This paper introduces a framework (including planning, execution, analysis, and modeling) for a data-driven evaluation of micro-mobility vehicles. The framework leverages our experience assessing bicycle dynamics in real traffic to make objective and subjective comparisons across different micro-mobility solutions. In this paper, we use the framework to compare bicycles and e-scooters in field tests. Results: The preliminary results show that e-scooters may be more maneuverable and comfortable than bicycles, although the former require longer braking distances. Practical Applications: Data collected from e-scooters may, in the short term, facilitate policy making, geo-fencing solutions, and education; in the long run, the same data will promote the integration of e-scooters into a cooperative transport system in which connected automated vehicles share the urban space with micro-mobility vehicles. Finally, the framework and the models presented in this paper may serve as a reference for the future assessment of new micro-mobility vehicles and their users’ behavior (although advances in technology and novel micro-mobility solutions will inevitably require some adjustments)