The potential of social routing advice

Travel information is expected by many scholars and practitioners alike to be successful in reducing traffic congestion and thereby improving road network efficiency. Yet, traditional (personalized) travel information aims at generating benefits to individual travellers, stimulating their personal optimization of their own route choices; it is well-known that this may lead to an inefficient user equilibrium. Examples on network efficiency have shown that in order to achieve system optimal network conditions, at least some travellers need to act non-selfish and take a detour to the benefit of others (i.e. the network as a whole). An important question in this regard is how to motivate those travellers to take this detour. This thesis deals with the problem of improving road network efficiency by stimulating social choice behaviour using social routing advice. Stated choice and revealed choice experiments provide insights into individual compliance behaviour, while network simulation indicates the resulting network impacts. Results show that travellers are sometimes willing to choose the social detour over their usual route. Travellers are willing to choose the social route when travel time sacrifices are not too large, when information messages are aiming at alleviating congestion as opposed to safety or environmental concerns, and when these messages are framed according to certain strategies that nudge travellers towards the social route, that reinforce social norms towards taking the social route or that educate travellers on the importance of taking the social route. Moreover, travellers are most likely to comply with the received advice when they are cooperatively oriented and when they make their choices in a non-habitual manner. As a result, network efficiency improves; structural congestion and unstable flows reduce, especially on major city roads. However, individual benefits will be marginal; the majority of travellers experience a travel time gain of less than two minutes. Finally, I show that the lower the compliance among travellers, the more social travellers need to compensate for the selfish behaviour of others by taking longer detours