The research and academic communities as well as the various research and development projects have examined urban mobility from various standpoints. A brief overview of the most relevant and notable efforts is presented next classified in thematic topics.
The role of spatial planning and land use
In their research, Meurs and Haaijers  contributed to the clearer understanding of the extent to which the spatial structure and planning of the residential environment can explain mobility, in general, and the choice of transport mode, in particular, and what planning and traffic management aspects play a significant role in this. Their research demonstrated that mobility and the choice of transport modes are directly linked with the characteristics of the spatial environment. According to their conclusions, the “impact of the characteristics arising from the residential environment is considerable at 20%, although this relative effect differs by mode of transport, from about 10% for car trips to 40% for journeys on foot” .
In a similar direction, Schwanen and Mokhtarian  studied the degree to which commute mode choice differs by residential neighborhood and by neighborhood type dissonance. The authors found that “neighborhood type dissonance is statistically significantly associated with commute mode choice: dissonant urban residents are more likely to commute by private vehicle than consonant urbanites but not quite as likely as true suburbanites” .
The consortium of the European project TRANSPLUS  was concerned with best practices about the integration of transport and land use plans and policies towards sustainability. It created a framework for the analysis of land-use and transport case studies in Europe and experiences of real-life planning initiatives.
The PLUME project created a thematic network for the optimization of scientific networking, management, co-ordination, monitoring, exchange of information and exploitation and dissemination activities with main mission the integration of land-use and mobility planning, involving a variety of stakeholders from the research community to local experts in the cities of Europe .
The wider environment (external factors)
Goldman and Gorham  examined the concept and implementation of sustainable urban transport. According to this research, to be successful, “sustainable transport policy must avoid the common transportation policy pitfall of ignoring the larger systems in which transportation activity is embedded”. Innovation is a key contributor in achieving sustainable transportation. The authors recognized four emerging areas of innovation: New Mobility, City Logistics, Intelligent System Management, and Livability.
Taylor et al.  conducted an interesting cross-sectional analysis of transit use in 265 urbanized areas in the US and constructed two-stage simultaneous equation regression models to account for simultaneity between transit service supply and consumption. The most important finding of their analysis is that four general factors outside the control of public transport systems explain most of the variation in transit ridership in urbanized areas: regional geography, metropolitan economy, population characteristics and auto/highway system characteristics. Another interesting result of their survey is that fare levels and service frequency could account for at least a doubling (or halving) of transit use in a given urbanized area. According to the authors, “the observed influence of these two factors is consistent with both the literature and intuition: frequent service attracts passengers, and high fares drive them away” .
Nicolas et al.  applied the theme of sustainable development to the case of urban transport and daily mobility of the inhabitants of a city to verify the feasibility and the usefulness of elaborating such sustainable mobility indicators. The authors propose a set of indicators, which simultaneously takes into account the three dimensions of sustainability - environmental, economic and social.
Market segmentation and user oriented approaches
Cherchi and Cirillo  used panel data to estimate a mode choice model that accounts for systematic heterogeneity over individual preferences and responses, and correlation across individuals over three time periods and across individuals and members of the families over six weeks. Their results suggest that “individual tastes for time and cost, and in particular the subjective value of time (SVT) point estimates, are fairly stable but there is a significant systematic and random heterogeneity around these mean values and in the preferences for the different alternatives” .
In their work aiming to develop an attitudinal market segmentation approach to mode choice and ridership forecasting, Outwater et al.  concluded that “individuals more aware of environmental issues are more motivated to use public transport, while on the contrary travelers more sensitive to stress tend to prefer car over public transport for non-work trips”.
Siddall et al.  conducted a user-centered design research to better understand how people use transit products and services throughout Northeastern Illinois, and to facilitate future improvements. Their targeted research produced detailed information about the characteristics and goals of users of various information products, how they are using the different sources, and what modifications might best serve specific customer needs. Furthermore, their “foundational research findings are more general and comprehensive in nature, and will inform and guide future efforts to establish regional information design standards for transit” . In a similar context, Minser and Webb  explored the influencing factors of public transportation customer loyalty using structural equation modeling. One of their most important findings is that passengers’ preconceived knowledge about a transit agency greatly influences their assessment on service delivery and value. For example, poor agency communication with stakeholders may negatively affect service ratings.
In their survey conducted in the San Francisco Bay Area in 1998, Collantes and Mokhtarian  explored the determinants of individuals’ subjective assessments of their mobility. Their study provides insight into the way individuals mentally process the amount of travel they do, which will increase the understanding of travel behavior and its motivations. A variety of personal factors were found to significantly influence such assessments: personality traits, travel-related attitudes, lifestyle characteristics, and affinity for travel.
Transport demand and travel behavior
The driving factors of passenger transport were examined by de Jong and van de Riet . Their research aimed at (re)structuring the many different insights in a single conceptual model, reviewing the key drivers, and how each affects the various choices that travelers make (activity type, destination, mode, time-of-day and route) and the resulting impact on overall passenger transport demand. According to their conclusions, the most important determinant of passenger transport demand in total, and of kilometres by car in particular, is household disposable income. The authors highlight that the availability of private modes (car ownership) is crucial as well, but their future development depends to a large extent on income growth.
Peirce and Lappin  assessed the levels of awareness and use of low- and high-tech sources of traveler information in a panel survey of Seattle-area residents. The authors found that despite large increases in respondents’ access to mobile phones and the Internet frequent use of traveler information is still largely concentrated among employed commuters, who tend to use conventional radio traffic reports.
Fujii and Taniguchi  reviewed the literature on travel feedback programs (TFPs), involving soft measures designed to change travel behavior, mainly from automobile to non-automobile travel, in mobility management. They classified TFPs using four main factors: place, technique, procedure, and communication media, and reviewed the effectiveness of 10 TFPs in Japan. They found that “TFPs reduced CO2 emissions by about 19% and car use by about 18%, while increasing the use of public transport by about 50%” .
Transit integration to other modes
Bos et al.  conducted an analysis using a Context-Dependent Hierarchical Choice Experiment to examine the choice of Park and Ride (P&R) facilities. Their results indicate that “safety, quality of public transport and relative travel times by transport modes are key attributes to the success of P&R facilities. Contextual variables seem to have only a minor impact” . Bos et al.  used a P&R choice model to assess the impacts of policy measures on P&R choice. According to their research, “the implementation of combined policy measures to improve the quality of both the P&R facility and the connecting public transport and to discourage car drivers to use their car for door-to-door trips have large, positively effects on the use of the P&R alternative” .
The integration of cycling to public transport has received major attention in recent years by researchers worldwide. Bachand-Marleau et al.  conducted a survey in Montreal exploring the potential integration of the local public bike-sharing system with transit. According to their results, bringing the bicycle onboard the transit vehicles is the preferred form of integration followed by bike&ride schemes. In the same context, Krizek and Stonebraker  described and evaluated four common bicycle and transit integration strategies and assessed their cost-effectiveness. Their results confirm the findings of the previous researchers, since cyclists prefer the bicycle onboard transit strategy. However, enhancing bicycle parking at a transit stop proved more cost effective when compared against bicycle onboard transit configuration.
Know-how and best practices transfer
The establishment of mobility centers in urban areas aiming to facilitate commuters’ and travelers’ mobility is one of the measures that has gained recognition in recent years. In this context, the recently completed project MOBI-NET aimed at creating a European Network of know-how on sustainable mobility promoting the concept of mobility centers. The purpose of the know-how transfer among mobility centers is to learn from each other and to optimize the implementation of local actions. The project produced a guidebook for setting up a mobility centre .
The SMILE project aimed to help local authorities cope with the challenge of reconciling citizens’ mobility needs with quality of life and environment by presenting good practices and introducing innovative approaches on a permanent basis . The project compiled the results and experiences of European cities and towns in designing projects and measures according to the needs of specific target groups and presented successful models on how to involve citizens.
Innovation and guidance for the implementation of measures
The mission of the NICHES project was to stimulate a wide debate on innovative urban transport and mobility between relevant stakeholders from different sectors and disciplines across Europe . NICHES promoted the most promising new concepts, initiatives and projects, to move them from their current ‘niche’ position to a ‘mainstream’ urban transport policy application. Some of the innovative concepts promoted by this project refer to Call-a-bus Services, Biogas in Captive Fleets, Public Bicycles and Urban Lift-sharing Services.
In order to assess mobility management measures, a Monitoring and Evaluation Toolkit (MET) was developed within the MOST research project. MOST-MET offers a step-by-step guide to what one should do in the monitoring and evaluation process of the mobility management measures that one plans to implement . It includes both a way to describe the measures (and the rationale for their selection) and the means to build-in a Monitoring and Evaluation process to assess impacts once the measures are implemented.
In addition to the above projects, EPOMM (the European Platform on Mobility Management, http://www.epomm.eu/) provides a forum for all those interested in mobility management: representatives from EU member governments and other European countries, local and regional authorities, knowledge institutes, universities, researchers, transport operators and other user and interest groups. EPOMM developed itself as a strong, co-operative and balanced network of all actors involved in mobility management in Europe, which provides a well-known network and reference point for all interested actors .
Additional knowledge in the field has been developed in other countries around the world, such as the innovative mobility management project conducted by MIT , which has issued reports about best practices implemented worldwide and has recently started the Future Urban Mobility initiative within the SMART research initiative in Singapore (http://smart.mit.edu). A second initiative carried out in the U.S. is the Innovative Mobility Research (IMR) group . IMR is based at the Transportation Sustainability Research Center (TSRC) at the University of California, Berkeley, and the current research areas include: goods movement, intelligent transportation systems (ITS), transit connections, mobility for special population groups, and alternative land use and transport futures. IMR designs research projects and conducts evaluations throughout the State of California, the U.S.A., and internationally.
The summary of the literature and state-of-the-art review provided above testifies that extensive and outstanding academic and R&D efforts have been made worldwide. They have derived models, systems, methodologies, techniques, guidelines and awareness campaigns addressing different aspects of mobility management. Their ultimate objectives are to contribute to innovation and to create a sustainable urban mobility, as well as to make public transport systems and services more suitable to the transport demand profiles of the cities.
According to the review, particular attention has been paid to the relationship between the spatial environment and urban mobility, and mainly the choice of the transport mode. The external factors that affect and explain the variation in transit ridership have been addressed, as well as the driving factors of passenger transport. The needs and preferences of particular market segments and user groups have been thoroughly examined. More focused research has also been conducted on traveler information systems, Part & Ride schemes and others.
The present paper adds another dimension to the existing literature. Using statistical methods, the paper contributes to a better understanding of the factors effecting commuters’ choice in the use of transport modes and the main reasons that discourage them in using public transport. The research demonstrates how probit and structural equation models, as well as additional statistical analysis can be used to gain better insight of the commuters’ mobility behavior and to apply adaptive and more effective mobility management policies. The gender- and age-based market segmentation analysis will shed further light on the mobility behavior of specific target groups.