| 1. |
- Hansson, Joel
(författare)
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Regional public transport : The balancing act of service planning
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis addresses the demand for more knowledge regarding regional public transport (between urban areas or to and from rural areas). More specifically, the aim is to develop a better understanding of the effects of different service planning decisions in terms of different trade-offs and their impacts on the overarching objectives of public transport provision. The studied trade-offs concern, for example, stop spacing in rural areas and the distribution of departures between peak hours and periods of lower travel demand.The thesis includes four research papers with different orientations relative to the overarching aim. The first paper is a literature review that explores preferences in regional public transport and how different quality attributes influence modal choice, demand, and customer satisfaction. The other three papers contain in-depth studies of some regional rail, coach, and bus services in the southern Swedish region of Scania, employing different research setups and statistical analyses to enable detailed examination of some important aspects of the service planning trade-offs.The results suggest that the trade-offs can be more complex than they may seem. For instance, stop spacing is commonly debated and assessed as a trade-off between travel time and spatial coverage. However, the results of this thesis demonstrate that stop spacing on regional bus services is not so much about travel time as it is about reliability. This is particularly evident for rural bus stops where buses rarely need to stop to pick up or drop off passengers. Also, the coverage aspect of the trade-off is complex, as higher service quality extends the catchment areas around the stops, not least by increasing the use of bicycles and cars as access modes.Regarding the distribution of departures between peak and off-peak periods, the results of this thesis show that reasonable off-peak service levels are valuable not only for providing possibilities to access activities beyond school and work, but also for attracting new patronage. Despite low patronage levels on some off-peak departures, such departures may contribute substantially to the overall patronage.The main contribution of the thesis is twofold. First, it sheds light on the balancing act that public transport service planning entails. Second, it highlights the regional perspective and shows that the differences between local and regional public transport affect the trade-offs that exist at the core of service planning.
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| 2. |
- Johnsson, Carl
(författare)
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Surrogate Measures of Safety with a Focus on Vulnerable Road Users : An exploration of theory, practice, exposure, and validity
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Surrogate measures of safety (SMoS) are meant to function as tools to investigate traffic safety. The term surrogate indicates that these measures do not rely on crash data; instead, they focus on identifying safety critical events (or near-crashes) in traffic, which can be used as an alternative to crash records. The overall aim of this thesis is to explore which SMoS are suitable when analysing the safety of vulnerable road users (pedestrians and cyclists). The thesis attempts to answer this question using two different approaches: 1) a literature review focusing on existing surrogate measures and how well they consider vulnerable road users from a theoretical perspective, and 2) four observational studies which focus on the validity of SMoS and their relation to exposure.The literature review focuses on identifying existing SMoS, and on two main aspects when evaluating their suitability for analysing the safety of vulnerable road users. Firstly, if the indicators theoretically are able to measure both the risk of collision and the potential for injury should a collision occur, and secondly, to what extent vulnerable road users were included in previous validation studies. The findings from the literature review are that the most commonly used indicators (Time to Collision Minimum and Post Encroachment Time) are also the most validated, but that they have several theoretical limitations, mainly that they to do not measure injury potential and that they measure the severity of an event based on the outcome rather than the initial conditions or potential/observed evasive actions. There are also several indicators which theoretically are more suitable but instead lack validation studies.The observational studies, which make up the second part of this thesis, consist of an attempt at a large-scale validation study, followed by several studies which focus on the shortcomings discovered in the first attempt. The large-scale study is based on three weeks of video recordings made at 26 signalized intersections in seven European countries. The analysis of these videos resulted in three major findings. Firstly, the lack of comparable crash records made any large-scale validation attempts impossible. Secondly, the lack of comparability between the critical events identified by human observers and those identified by computer calculations made it infeasible to perform a long-term analysis. Thirdly, there is a significant relationship between meetings and critical events identified using Time to Collision Minimum and Post Encroachment Time, which suggests that some of the benefit of using those (and other indicators) might originate from their inherent connection to simple meetings between road users (i.e. exposure). Following these results, the thesis presents a limited validation study based solely on the Scandinavian intersections followed by a suggestion for how a relative approach to validity might offer a potentially easier way of evaluating SMoS in the future. The results from these studies indicate that Time to Collision Minimum can measure safety to at least some extent, while Post Encroachment Time measures it to a lesser extent. Due to the strong connection between critical events and meetings, the thesis also explores how a meeting between road users can be defined and how understanding what constitutes an opportunity for a crash might help to explain the so-called safety-in-numbers effect, as well as how future SMoS studies should consider meetings.
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| 3. |
- Kuipers, Ruben
(författare)
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Dwell time delays for commuter trains : An analysis of the influence of passengers on dwell time delays
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis presented here delves into why dwell time delays for commuter trains occur, with a specific focus on the impact of boarding and alighting passengers. The overarching aim is to develop knowledge of how time delays arise to identify and describe potential ways in which dwell time delays can be reduced. In addition to this, a secondary aim is to identify how dwell times can be studied on a network-wide level. Six research papers are included in this thesis, which all contribute to the aforementioned aims. The first paper presents a literature review on the influence of passengers on dwell times. The five subsequent papers present different data analyses on the impact of passengers on dwell times and make use of several years worth of automatic passenger count data collected on board commuter trains in Stockholm and the region of Skåne in Southern Sweden. The findings from these studies indicate that although the volume of passengers is often stated as the main cause for dwell time delays, this is not necessarily the case. The results, instead, suggest that the volume of passengers acts as an accelerator for the negative impact of other aspects of the dwelling process such as the behaviour of passengers. With regards to studying dwell time delays it is important to make use of robust measures and to presentdwell time delays in terms of frequency and size rather than just an average value. In addition to this, the value of having data on a level of seconds rather than minutes is highlighted. The latter is important since a majority ofdwell time delays are smaller than one minute. Several avenues to reduce the risk of dwell time delays are proposed, based on the findings from the includedstudies. The first avenue to be explored is that of adopting a more dynamic approach to dwell time scheduling. In practice, this means that, in contrast to what is common practice in Sweden, different dwell times should be usedduring peak and off-peak hours and between different stations. In addition to this, it is important to account for the behaviour of passengers during the boarding and alighting process. This can be done by making use of platformmanagement measures. The third avenue that is identified states that dwell time scheduling should take on a more network-wide approach rather than treating stations as a single entity. This is important since there are interdependencies between stations that influence the behaviour of passengers, such as the way passengers spread out. Working on these points will help to reduce the risk of dwell time delays. Although this thesis has an emphasis on the Swedish context, given the origin of the data, the above-mentioned avenues are likely to be applicable in different geographical settings as well.
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| 4. |
- Palmqvist, Carl-William
(författare)
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Delays and Timetabling for Passenger Trains
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Travel by train has increased steadily in Sweden the last 30 years. The pace has been about two to three percent per year, and we now have twice as many passengers. With growing awareness of the changing climate, the pace is increasing further. A problem that affects both passengers and businesses in Sweden is train delays. One way to describe these is as the share of trains that arrive less than six minutes delayed. About 90% of trains in Sweden meet this standard and have done so for many years. In a way this is impressive, since there are now many more trains. Unfortunately, this also means that more and more passengers are affected by delays. This leads to irritation, threatens the shift of traffic to railways, and costs a lot for society. More trains must arrive on time. This thesis shows that delays are mostly caused by small disturbances – up to a minute or two. Over long journeys, these small disturbances accumulate and sometimes cause quite big delays. These delays mostly occur at stations, where the trains stop, but are then unable to continue on time. It is difficult to say exactly what causes these small disturbances, but the time that the trains are supposed to be at stations – the dwell times – are often too short. Another pattern is seen between delays and weather: if it is either warm or cold, delays increase rapidly. And while winter and snow return every year, they still cause major disruptions. The thesis holds a few suggestions to reduce delays. One is platform markings that show where the trains will stop, where the doors will be, and where the passengers should wait. This is an easy and affordable way to speed up the stops, so that the trains depart on time. Another measure is to remove switches. Then there are fewer parts that can fail, and those that remain can be maintained to a higher standard. A third way is to adapt the railway, so that it better withstands the weather variations of today, and the climate changes of tomorrow. Something that has been done in other countries is to shade and air-condition electronics and signals along the railway. Then the components to not overheat, and more trains run on time. Many things can also be done with timetables, so that more trains run on time, without a rise in costs. More of the planning can be automated. Then more time can be spent on giving trains appropriate dwell times. Infrastructure managers should also do more to evaluate and improve the rules and guidelines that govern timetabling. In this way we can improve timetables gradually from year to year, with fewer and fewer delays as a consequence. These suggestions do not solve all of the railway’s issues, but they would lead to many more trains arriving on time.
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| 5. |
- Bagdadi, Omar
(författare)
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The development of methods for detection and assessment of safety critical events in car driving
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Improving our knowledge of drivers’ behaviour, especially in hazardous situations is a key to understanding why accidents occur and how to improve safety on our roads. Crash surrogate measures have proven to be very useful in traffic safety analysis. As a valid crash surrogate measure shares the same logical chain of events as actual crashes, studying those events increases the opportunities to analyze external circumstances as well as events and driver behaviour preceding the crash. A new definition of crash surrogate measures is proposed, i.e. safety critical braking events: Situations (including crashes) that require a sudden, evasive manoeuvre to avoid a crash or to correct for unsafe acts performed by the driver himself/herself or by other road users. This thesis develops a method for detecting Safety CRItical Braking Events (SCRIBE) and evaluates against other methods mostly used in large naturalistic driving studies. The evaluation shows promising results in the success rates of detecting safety critical events. Further, a Method for estimating the SEverity of safety Critical events (M-SEC) involving more than one road user, is developed and evaluated. The method combines a measure of closeness-to-collision, or safety margins, with a measure of possible consequences based on the speed and mass of the involved road users. Besides, a comparison is made with the Traffic Conflict Technique. Evaluation of the method shows that the estimated severity using M-SEC enables comparison of safety critical events involving different types of road users and is not limited to comparisons between similar types of events. In addition, the estimations when using M-SEC seem to reflect the seriousness of the safety critical events.
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| 6. |
- Hammad, Samir, et al.
(författare)
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Kollektivtrafikens sårbarhet i Covid-19-eran : En holistisk strategi framåt
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The role of public transport in society is crucial, particularly for those who do not have access to alternative transport modes. For public transport to be able to fulfil its societal role, it should not be perceived as unsafe or unhealthy by its (potential) users. Several studies from all over the world have shown that anxiety has increased remarkably during the pandemic, and it is likely to last much longer. Furthermore, the pandemic is expected to affect travel behaviour even when it will be over and all the restrictions will be lifted due to, among other things, increased teleworking, increased unemployment and the remaining effect of concerns about congestion and infection. This study aims to investigate how the public transport supply has adjusted during the different stages of the pandemic and what the result of these changes on the costs of public transport has been. The study also aims to identify today's challenges, the measures that have already been implemented and what needs to be done in the future to keep public transport functioning in similar circumstances and to help it recover quickly and fully after the pandemic. The method used to understand the pandemic's impact on public transport and thus be able to answer the study's first two questions, is a literature study. Thereafter, quantitative data on ridership, public transport supply and costs have been collected. The data has been analyzed and visualized to present it in an easy-to-understand way. To answer the final question about how to better adapt public transport to the covid-19 pandemic in the medium and long term, qualitative interviews have been conducted. Finally, the proposed strategies presented in this paper have been assessed using the multi-Criteria Analysis.
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| 7. |
- Koglin, Till
(författare)
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Vélomobility - A critical analysis of planning and space
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this doctoral study is to bring a spatial dimension into the research on urban mobilities and connect the spatial dimension to the marginalisation of cyclists in urban space. This is been done by exploring the role of urban bicycling and transport planning. The theoretical frame of space, mobilities and power is used for analysing that role through case studies in two Scandinavian cities, Copenhagen and Stockholm. Urban bicycling is a good example of showing the relation between space and mobilities, since cyclists often suffer from marginalised space in cities around the world. The philosophical foundation of the thesis is in critical realism and critical theory. For background data, observations and document studies have been conducted in Stockholm and Copenhagen. The main data collection for this thesis was done both qualitatively, in the form of interviews with planners and politicians, and quantitatively, in the form of survey studies among the citizens of Copenhagen and Stockholm. The data is analysed with the help of the theoretical framework that builds on mobility studies, spatial theory by Lefebvre, and Harvey and power theories deriving mainly from Lukes’ three dimensions of power. The materialisation of power relations is analysed with the example of modern planning in Sweden and Denmark. Overall this thesis manages to show how cycling as a mode of transport is marginalised in urban space, and that urban space wars between cyclists and car drivers and among cyclists are fought in Copenhagen as well as in Stockholm. The conclusion is that different factors, such as the economic situations in Denmark and Sweden, have affected urban and transport planning and thus have created two very different transport systems, where cycling plays a large role (Copenhagen) and a smaller role (Stockholm). Nevertheless, this thesis shows that even in cities that are very good for cycling, like Copenhagen, the motorised modes of transport create many problems and are still dominating urban space.
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| 8. |
- Manan, Marizwan
(författare)
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Factors Associated with Motorcylists' Safety at Access Points along Primary Roads in Malaysia
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- More than 50% of road accident fatality victims in Malaysia are motorcyclists, numbering more than 4,000 fatalities per year. The aim of this thesis is to investigate motorcyclists’ road safety problems in general in Malaysia, and narrow down the focus to the most salient road infrastructure related risk factors. After identifying access points on primary roads as hazardous sites, observations of road user behavior at these sites have been carried out in order to establish behavioral and design factors associated with a hazardous outcome of interaction between motorcyclists and other road users. The data collected for this thesis ranges from accident records to on-site observational data including speed and behavior. The method ranges from cross-sectional analysis of accident data to advanced statistical modeling. The thesis finds that Malaysian road accident statistics suffer from disproportional underreporting of severe injuries. A motorcycle Safety Performance Function estimates that an increase in motorcycle fatal accidents per kilometer is highly associated with an increase of access points per kilometer and the average traffic volume of motorcycles. The observational study has detected a hazardous right turning movement, i.e. the Opposite Indirect Right Turn, which is performed by 18% to 26% of right turning motorcyclists entering a primary road from an access point. Moreover, motorcyclists entering the primary road are involved in serious traffic conflicts to the same extent as other vehicles. The advanced statistical analysis shows that the outcome for motorcyclists involved in a serious traffic conflict is influenced by their manner of entry into the primary road from the access point, their stopping behavior and the lane width of the primary road. Overall, this thesis shows the importance of identifying motorcyclists’ behavior, as well as road environment attributes, in order to understand the road safety situation of motorcyclists.
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| 9. |
- Sulejmani, Pajtim
(författare)
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Climate impact on the durability of asphalt concrete
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Roads are subjected to traffic loads and varying climate conditions that eventually lead to different types of damage. Moisture in asphalt is one of the major causes of premature failure in asphalt pavements. In addition, moisture in the unbound layers and temperature in the asphalt concrete (AC) layers affect the structural response of pavements under loading, such as the tensile strain at the bottom of AC layers. This thesis focused on identifying the influence of climate on the deterioration of flexiblepavement and on the assessment of pavement performance with regard to variations of temperature and moisture content. Laboratory testing of AC with various mix compositions under repeated pore pressure loadings to quantify the influence of mixcomposition against moisture sensitivity was performed. The influence of climate parameters, i.e. moisture content and temperature on the tensile strain at the bottom of the AC layer, was also studied by means of a falling weight deflectometer andresponse measurements at full-scale pavement test sections. The results showed that binder content, air void content and pore pressure conditioning have a significant influence on the stiffness reduction of AC. In addition, the temperature and moisturecontent have yielded significant contributions towards explaining the strain at the bottom of AC layers. Relationships between climate impact and asphalt pavement properties have been proposed which may be useful in the evaluation and design offlexible pavement with respect to climate conditions.
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| 10. |
- Waara, Nina
(författare)
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Traveller information in support of the mobility of older people and people with disabilities. User and provider perspectives.
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Traveller information designed to fulfil needs and expectations of individual travellers is a key factor in improving access for older people and people with disabilities to public transport. The overall aim of this thesis is to contribute to the knowledge of user and provider perspectives on the provision of traveller information for older people and people with disabilities in public transport with a focus on use and provision of such traveller information through online traveller information services. The research work is based on perceptions of older people and people with disabilities, together with experts’ views on the implementation process. Both qualitative methods (interviews, focus group interviews, group discussions, workshops) and quantitative methods (questionnaires) were used. The substantial influence on the travel of older people and people with disabilities of use of online traveller information services is the empowerment of those of the older travellers and travellers with disabilities that are anxious and insecure before a journey. Through better access of traveller information offered by online traveller information services these travellers can find what they need to build their confidence before a journey and subsequently be supported in their roles as travellers. That is, when they do travel in public transport they want to be able to do so safely and with confidence; they do not necessarily want to increase the number of journeys they undertake. Thus, theoretically the concept of motility has higher relevance for this particular group of travellers than the concept of mobility. The exploration of the traveller information content shows that even though the need to plan and prepare for a journey seems to be equally important for the whole group of older people and people with disabilities as it is for subgroups based on functional limitations, the importance and the intended use of the traveller information differ between groups as the focus shifts from comfort information on an aggregated level to an increasing importance of accessibility information for subgroups. Both the comfort information and the absolute information enable assessment of the effort required to carry through a journey. This is decisive for the choice to travel, but the traveller information focused on comfort relates more to the individual choice to travel while absolute traveller information enables the traveller to assess whether travel is possible at all. Finally, to be accessed the traveller information needed by older people and people with disabilities need to be implemented. The inertia of the implementation process was explored through conflicts of interest that can help forward barriers in the implementation process. The findings point to there being a verbal problem in policies, legislation and guidelines that leave room for interpretation of the necessity of implementation of measures like traveller information needed by older people and people with disabilities. Finally this thesis carries implications for further research within all three areas that have been researched.
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