Torres, A.; Oliete, S.; Magrinya, F.; Gauthier, J. Transportation research. Part A, Policy and practice Vol. 107, p. 216-228 DOI: 10.1016/j.tra.2017.11.016 Data de publicació: 2018-01 Article en revista
Road conditions in Sub-Saharan Africa are typically poor, and only a subset of the newly constructed or rehabilitated roads reach their design life. Truck overloading generally causes this rapid deterioration. In Africa, there are few success stories on the imposition of axle-load limits. This study examines the existing regulations on the Douala-N'Djamena international road, which is the main transport corridor in Central Africa and the backbone for internal transport in Cameroon. It benefits from the detailed existing weighing data recorded since 1998 in the corridor's 10 weighing stations. This vast amount of traffic data, together with available information on road structure and deterioration over time, has been used to conduct an accurate calculation of load equivalency factors. The HDM 4 model has been applied to three scenarios between 2000 and 2015: (1) no axle-load control, (2) the real situation and (3) no overloading tolerance. Results show that axle-load regulations have been reasonably well applied in Cameroon and have contributed to maintaining the corridor in fair condition. In spite of the fact that significant traffic increases are presently counterbalancing the damage avoided by axle-load limits, benefits provided by axle-load control have been substantial: in the period of 2000–2015, every € invested or spent on axle-load control has generated more than €20 of savings in road user costs and in road maintenance and rehabilitation expenditure, which represents, in absolute terms, more than €500 million.
Conventional wisdom states that transit riders are averse to transfers and that consequently bus networks should be designed to limit their number. Probably as a result of this belief, many real bus systems try to connect as many origins and destinations as possible without transfers, so they are usually composed of long, circuitous routes with redundant overlapping sections – and the resulting bus map is hard to understand. If coverage is extensive, many routes are needed. Economics then prevents an agency from populating all routes with sufficient buses to provide attractively frequent service. This low frequency and the complicated circuitous map discourage transfers, perpetuating the belief that people are averse to transferring. Not surprisingly, the percentage of bus trips that includes a transfer has been reported to be: 1.5% for Boston, 3% for New York, 13% for London, and 16% for Melbourne. The Nova Xarxa in Barcelona was designed with a different paradigm. It was designed and deployed to cover the whole city on the belief that if a bus map is easy to understand, and has direct lines with frequent service and ubiquitous transfer points then the bus system would become more appealing, people would transfer more freely and become users of the network rather than its single lines. With this design paradigm, a city can be covered with fewer lines, which can be depicted on a simple map. The lines can in turn be economically populated with sufficient buses to deliver the high frequency required to encourage transfers. Could this work? To answer this question and see whether there is truth in the beliefs underlying the new paradigm, this paper examines data from the first three deployment phases of the Nova Xarxa (from 2012 to 2015). It is found that the Nova Xarxa is already attracting more demand than the network it replaced. This attests to its appeal. Furthermore, this demand has increased disproportionately with the number of lines opened for service in each phase, revealing that some people are using the Nova Xarxa as a network. The paper further shows that this growth is underpinned by transfers - at the end of 2015, the percentage of trips that involved a transfer was approximately 26%, and it reached a maximum of 57% for line V7. These numbers should increase considerably (to 44% and 66%, respectively) once the Nova Xarxa is completed in 2018 and passengers have even more opportunities for transferring. The numbers disprove the conventional wisdom. They strongly suggest that transit providers can attract more demand by providing transfer-friendly networks that can be used as such and not as an inefficient aggregation of individual lines.
After the widespread deployment of Advanced Traveler Information Systems, there exists an increasing concern about their profitability. The costs of such systems are clear, but the quantification of the benefits still generates debate. This paper analyzes the value of highway travel time information systems. This is achieved by modeling the departure time selection and route choice with and without the guidance of an information system. The behavioral model supporting these choices is grounded on the expected utility theory, where drivers try to maximize the expected value of their perceived utility. The value of information is derived from the reduction of the unreliability costs as a consequence of the wiser decisions made with information. This includes the reduction of travel times, scheduling costs and stress. This modeling approach allows assessing the effects of the precision of the information system in the value of the information.
Different scenarios are simulated in a generic but realistic context, using empirical data measured on a highway corridor accessing the city of Barcelona, Spain. Results show that travel time information only has a significant value in three situations: (1) when there is an important scheduled activity at the destination (e.g. morning commute trips), (2) in case of total uncertainty about the conditions of the trip (e.g. sporadic trips), and (3) when more than one route is possible. Information systems with very high precision do not produce better results. However, an acceptable level of precision is completely required, as information systems with very poor precision may even be detrimental. The paper also highlights the difference between the user value and the social value of the information. The value of the information may not benefit only the user. For instance, massive dissemination of travel time information contributes to the reduction of day-to-day travel time variance. This favors all drivers, even those without information. In these situations travel time information has the property that its social benefits exceed private benefits (i.e. information has positive externalities). Of course, drivers are only willing to cover costs equal or smaller than their private benefits, which in turn may justify subsidies for information provision.
Estrada, M.; Roca-Riu, M.; Badia, H.; Daganzo, C.F.; Robuste, F. Transportation research. Part A, Policy and practice Vol. 45, num. 9, p. 935-950 DOI: 10.1016/j.tra.2011.04.006 Data de publicació: 2011-11-11 Article en revista