Dutch municipalities are increasingly reclassifying urban distributor roads from 50 km/h (GOW50) to 30 km/h (GOW30). For this policy to succeed, speed limits must be credible (i.e., aligned with drivers’ expectations formed by the visual and physical cues of the road). This study examines how road design features shape (i) actual vehicle speeds and (ii) drivers’ perceptions of speed limit credibility and safety. A mixed-methods design combined objective speed measurements from 30 urban road segments in the Netherlands (600 observations; 70% at 30 km/h) with a perception survey (n=83). For speeds, descriptive analysis, t-tests/ANOVA, and a General Linear Model (GLM) were used; perceptions were analyzed using chi-square tests and Ordinal Logistic Regression (OLR). Key results: (1) Narrower lanes, brick surfaces, and the absence of bike lanes are associated with lower speeds; (2) in multivariate GLM, road surface, lane markings, bike lane configuration, and lane width are significant predictors; (3) credibility perceptions differ by context: Features that bolster a 30 km/h limit include brick surfaces, absent markings, and minimal/no bike separation, while a 50 km/h limit is seen as more credible when presented with asphalt surfaces and clearer separation. The findings
provide empirical support for self-explaining road design and argue for design-led speed
management to reinforce low-speed policy goals.

This study aimed at evaluating the effect of different types of external Human-Machine Interfaces (eHMIs) on cyclists’ crossing behaviour when interacting with an automated vehicle (AV) in a shared space. Using a Virtual Reality (VR) experiment, four eHMI designs (no eHMI, textual, symbolic and lights) were systematically tested throughout a series of crossing scenarios, in which participants engaged in the role of a cyclist using a VR bicycle simulator. Each design was tested under yielding and non-yielding conditions. Cyclist behaviour was recorded through objective measures, such as crossing initiation time, gazing time and crossing intentions, while subjective perceptions were captured in a post-experiment questionnaire. The results indicate that eHMIs do influence cyclists’ crossing behaviour, however not consistently across all behavioural metrics. The textual and light eHMI significantly decreased the crossing initiation time of cyclists when the AV is yielding, while the lights increased the crossing time and gazing time when the AV is not yielding. In contrast, any form of eHMI shows a significant improvement across all subjective measures, enhancing the perceived safety, trust and decision-making of cyclists. The symbolic eHMI consistently received the highest ratings, however, overall differences were minimal. Therefore, a gap is observed between the subjective perceptions and impressions of cyclists and their actual behaviour. This study contributes to the growing literature on cyclist-AV interactions, which is still underwhelming. It forms a solid basis for further research optimizing eHMI design for real-world implications. In addition, it proves that VR is an effective tool for analyzing these interactions in realistic yet controlled environments.

Airside service roads are essential for the movement of ground support vehicles that enable efficient aircraft turnaround and overall airport operations. Despite their importance, no standardised method exists for evaluating their capacity and performance, limiting the ability of airports to optimise this operational infrastructure. However, the heterogeneity of service road traffic — characterised by vehicles with varying speeds, sizes, and manoeuvrability — complicates capacity estimation and Level of Service (LoS) assessment. This research shows that a combination of microscopic traffic simulation and Multiple Linear Regression (MLR) provides a robust framework for estimating Passenger Car Unit (PCU) values and evaluating service road performance. Using five common airside road configurations, the method estimates PCU values for eleven service vehicle types and establishes LoS boundaries expressed in PCU per hour. The results reveal that PCU values vary significantly across intersection types, with four-way priority intersections exhibiting the highest sensitivity to traffic heterogeneity. Roundabouts are found to facilitate smoother traffic flow. Two three-way intersection types provide similar PCU values, but traditional priority rules facilitate substantially better performance. The results of the component-level models are upscaled to a service road network model, presenting a method for describing network performance. These findings provide a standardised method for assessing airside service roads, enabling airports to improve infrastructure planning and mitigate congestion amid rising aviation demands.

Past bicyclist subjective safety studies have evaluated different intersection types and bicycle facilities at roundabouts. None have focused on the different design elements of a dedicated bicycle facility and analyzed both perceptions of safety and comfort of bicyclists in a single model. To address this, this study focuses on the subjective safety and comfort perceptions of bicyclists at Dutch urban roundabouts, focusing on certain bicycle design elements. Infrastructure evaluated included: bi-directional bicycle paths; yielding priority; bicycle volumes; the presence of art or advertisements in the center island; buffer width between the bicycle path and the vehicle lane;
and the number of vehicular entrance/exit points. Using a multivariate random effects ordered probit model, the results revealed that roundabouts where cars have to yield to bicycles and fewer vehicular legs are perceived as safer and more comfortable by cyclists. Conversely, high bicycle volumes and increasing age negatively impacted perceptions of safety. The study found that bicyclists’ place of residence, their likelihood to commit traffic violations, their recent crash history, and the type of bicycle used (e.g., cargo bicycle, e-bicycle, etc.) significantly affect their perceptions of safety. The results suggest that consistent adherence to Dutch design guidelines can enhance bicyclists’ sense of comfort and safety at roundabouts. The findings highlight the need for designers to consider bicyclists’ perspectives in roundabout design. To improve perceived safety and comfort for bicyclists recommendations include: ensuring bicycle yielding priority; designing roundabouts to reduce bicycle congestion to the extent possible; and maintaining uniformity in bicycle infrastructure.

Several incidents involving the installation of temporary traffic signs by road workers have raised concerns about the effectiveness of these signs. Even in the absence of incidents, effectiveness is a relevant question, made more urgent by the incidents and the high risk of collision faced by road workers installing the signs. This paper investigated the influence of static traffic diversion signs on drivers' route choice and driving behaviour during road closures on secondary roads adjacent to motorways in the Netherlands. The influence of static diversion signs is assessed by analysing route choice, detour compliance and changes in driving behaviour, in terms of speed variations around diversion signs. In addition, the paper aimed to develop a detour behaviour model that classifies drivers into four different detour driver profiles. These profiles are developed based on potential route choices, driving patterns around road closures, detour behaviour factors and driving styles. Therefore, the four driver profiles are categorised as following the detour, not following the detour, choosing an alternative route and avoiding the closure area. This model provided a systematic framework for understanding detour route choices and shows the complexity of driver behaviour around road closures. Two case studies are evaluated by an observation study on route choice, detour compliance and speed adjustments around detour signs, during night-time road closures. The first case study was conducted near exit 9 Aalsmeer on the A9 motorway and the second near exit 27 Hagestein on the A27 motorway in the Netherlands. Observations from the A9 case study showed that 73.8\% of the road users heading towards the closed road do not comply with the detour signs during the closure phase, which accounts for 18.3\% of the expected traffic on the exit ramp. A more detailed analysis of route choice in the A27 case study showed a 33\% compliance rate with the detour. A significant proportion of road users (60\%) showed non-compliance by disregarding signs and taking the shortcut. In addition, a small percentage (4\%) did not initially follow the diversion but later returned to the motorway to comply, while a further 4\% chose to avoid the closed road area altogether. Therefore, the non-compliance rate across both case studies ranges from 64\% to 73.8\%. The results showed that static signs have a limited effect on diverting traffic to the detour. Moreover, there are no significant changes in speed around the signs found, supporting a limited effect on changing driver behaviour. The paper highlights the complexity of driver behaviour around road closures and demonstrates the limited effectiveness of static diversion signs in directing traffic to detours. These findings emphasised the importance of re-evaluating sign placement and it is recommended to explore and implement alternative methods of traffic control. This could include the use of dynamic, real-time information, such as smart traffic systems and mobile applications, to guide road users more effectively and improve the safety of road workers. Future research should focus on individual-level road user and factor analysis, the influence of navigation systems, and the effects of temporary traffic measures in different contexts to further refine traffic management strategies.

The field of automated vehicles gains more and more attention each year as the effective implementation of such vehicles in real life is imminent. The increasing amount of scientific studies addressing the impact of automated vehicles on the traffic network shows the same trend. While much research focuses on regular intersections, only a few investigate the impact of turbo-roundabouts. In particular, studies researching the obtainable capacity increase on turbo-roundabouts under fully automated conditions are scarce. A turbo-roundabout is a multi-lane roundabout with separated lanes that require vehicles to choose their desired destination before entering the turbo-roundabout, effectively eliminating most weaving conflicts on the roundabout itself. Only a single paper researches how much additional merging capacity can be obtained by automated vehicles on a turbo-roundabout compared to human-driven vehicles (Fortuijn and Salomons, 2020). This study takes a theoretical approach and uses existing theory about turbo-roundabout capacity to generate five graphs depicting the merging capacity of the left lane of a minor access branch for varying circulating traffic volumes on the turbo-roundabout: four models for differing automated vehicle settings and one human-driven vehicle model. These four automated vehicle models differ in complexity, where the most complex model features gap synchronisation, headway optimisation, and path guidance. Each model, therefore, has different following distances, vehicle speeds, critical gaps, etc. The results of the theoretical models are capacity curves depicting the merging traffic capacity over the circulating traffic volumes.
This thesis investigates whether the capacity increase obtained from the most simplified automated vehicle model of the theoretical study can be obtained through microscopic traffic simulation in VISSIM. What must be noted is that the most simplified model of this theoretical study features communication between vehicles, which is not the case in the simulation models of this thesis. Therefore, higher follow-up times must be maintained in the simulation models, whereas the theoretical model uses minimal follow-up times to obtain a capacity increase of 58%. Initially, this thesis aimed to determine the achievable capacity increase for Connected and Automated Vehicles. However, due to limitations in VISSIM, the capacity increase could only be obtained for Automated Vehicles as the software cannot model communication between vehicles. Therefore, this report does not obtain the highest potential capacity increase for automated vehicles but serves as a stepping stone for more complex AV models. It determines the additional merging capacity of automated vehicles on turbo-roundabouts, only considering key parameters such as the car-following behaviour, critical gap and follow-up times. Gap synchronisation, an important aspect of the study of Fortuijn and Salomons, is not included in the simulation models due to shortcomings in VISSIM. Before making the AV models, this thesis aims to calibrate the VISSIM model for human drivers with real traffic data at a turbo-roundabout in Nieuwerkerk aan den IJssel, the Netherlands. Only when the VISSIM model is capable of accurately modelling human behaviour can it be used to determine the capacity increase through AVs. The thesis starts with developing a human-driven vehicle model to determine the merging capacity of the turbo-roundabout in current traffic conditions. The calibration is conducted on the traffic flow level through an iterative process where the critical gap and follow-up times are adjusted. The root-mean-normalised-squared error (RMNSE) determines the difference between regression lines of the merging capacities of the simulation model and the real traffic measurements. Based on the calculated differences between both lines, the critical gap and follow-up time parameters are adjusted.
For the left lane, the iteration process reduced the RMNSE from 0.427 to 0.072, equaling an improvement of 72.5%. For the right lane, the iteration procedure gave an unsatisfactory result. The RMNSE increased from 0.408 to 0.427, which signifies an increase of 4.7%. The final capacity curve after seven iterations was unrealistic. It was concluded that the VISSIM model performs adequately at simulating realistic behaviour on the left lane but that the same accuracy could not be achieved for the right lane. The calibration procedure is only applied to the minor branch of the turbo-roundabout as the data for the major branch could not be used for calibration. Subsequently, the calibrated model serves as the basis for developing three automated vehicle models: cautious, normal, and aggressive, each representing a different aggression level of automated vehicles. Each of these models features a different car-following model to simulate the various levels of aggression. Furthermore, the critical gap times of the human model are changed to model Avs properly, and for each of the three models, a penetration rate of 100% of AVs is applied. For each of the three automated vehicle models, this thesis measures the increase in capacity. It compares it to the theoretically obtained capacity increase of 58% for the left lane of the minor access branch of the turbo-roundabout. This thesis finds capacity increases of 7.47%, 38.62%, and 24.32% for the cautious, normal, and aggressive automated vehicle models, respectively. For the right lane, the obtained capacity increases were not calculated as the final HDV model is inaccurate for this lane. An unexpected result is that the normal automated vehicle model outperforms the aggressive model for the left lane, even though the parameter settings should result in a higher capacity for the aggressive model. Comparing the resulting capacity increases to the 58% increase of Fortuijn and Salomons, one can conclude that the simulation model does not reach the same increase in capacity as the theoretical model. This is not an unexpected result, as a theoretical simulation model has fewer interactions, and the theoretical model assumes communication between vehicles, whereas the simulation models do not. Therefore, concluding that the microscopic traffic simulation models in VISSIM cannot accurately model the behaviour of automated vehicles is premature. The models leave room for improvement by fine-tuning various parameters that were ignored in this thesis. This thesis concludes that, while VISSIM is adequate at simulating human-driven vehicles, it has various limitations for modelling automated vehicles. First of all, gap synchronisation and headway optimisation cannot be modelled, while these are the most critical elements to unlock the full potential of automated vehicles on turbo-roundabouts. If one wants to incorporate these into VISSIM, an external mathematical software package is necessary. Considering other software packages for studying (C)AVs on turbo-roundabouts is advised. This thesis is a foundation for future research on turbo-roundabouts, both for the calibration process and for simulating automated vehicles.

In the face of urbanization and limited space, traffic management grapples with challenges, especially heavy left-turn volumes at signalized intersections. The pre-signal strategy, proposed by Li et al. (2014), emerges as a promising solution. It involves an additional traffic light upstream of the main intersection, creating a "sorted area" where vehicles distribute before reaching the main intersection. Although simulation studies show increased intersection capacity with pre-signals, behavioral assumptions about drivers' spread behavior in the sorted area lack validation from behavioral science.

This study investigates drivers' behavior in pre-signalized intersections, addressing how their lane selection downstream of pre-signals impacts efficacy. The main research question is: How does drivers' lane selection downstream of pre-signals impact the efficacy of pre-signal implementation for regular traffic? A stated-choice experiment involved over 1000 respondents making preferred lane choices in diverse traffic conditions. Analysis using a MultiNominal Logit (MNL) choice model reveals crucial insights.

Results indicate that pre-signals don't alter drivers' perceptions of traffic crowdedness. However, discomfort with lane changes emerges as a critical factor influencing efficiency. Drivers strongly hesitate to execute multiple lane changes, posing challenges for achieving an equal spread in the sorted area.

Two implementation options are discussed: using the entire sorted area for all traffic or dedicating parts to specific traffic directions. Each option has efficiency and safety trade-offs. Designing a pre-signal system achieving both an equal spread and using the entire sorted area for all traffic proves unfeasible.

The study emphasizes integrating behavioral science into pre-signal studies, offering valuable insights for traffic engineers. It lays the groundwork for understanding pre-signals, highlighting the imperative for continued research and a holistic approach to their implementation.

Traffic congestion and undeveloped public transport define the modus operandi in Kampala, the capital city of Uganda. Most people see motorcycles as a solution to escape the growing traffic congestion and poor public transport. This study thus aimed to determine the traffic efficiency and safety effectiveness of introducing motorcycle dedicated lanes in non–lane based and mixed traffic. These effects were studied by microsimulation of unsignalized intersections without priority markings in urban areas of developing countries. The study centered on an intersection commonly known as “Spear Motors” in Kampala. In addition, off-peak traffic was simulated since traffic police controls the intersection during peak time and microsimulation model cannot simulate traffic while a policeman (or two) is on duty.
Video images of the intersection were officially obtained from Uganda Police and processed to traffic data such as traffic volume, trajectories, composition, and conflicts. In addition, geometric data (lane width, slope, intersection dimensions, coordinates, and aerial pictures) about the intersection was physically collected during a daytime site visit.
A representation of the current traffic conditions at the intersection, referred to as the base model, was developed in VISSIM 21. The base model was calibrated using Particle Swarm Optimization (PSO). Thereafter, the model was microscopically and macroscopically validated.
Three scenarios were considered in this study, which are: scenario 1 with straight crossings of motorcycles in the intersection, scenario 2 with deflected crossings and scenario 3 with a roundabout separated for the main road traffic and motorcycles.
Simulations with driver behavior parameters set to optimum values were performed to replicate the actual behavior. Consequently, traffic conflicts were generated from vehicle trajectories per scenario. Post Encroachment Time (PET) and Time to Collision (TTC) were calculated for the conflicts. The use of conflicts is proactive compared to reactive approaches that use crashes.
The use of deflected crossings for motorcycles and then a roundabout separated for main traffic and motorcycles increased the flow of the intersection by 31% and 20%, respectively. Additionally, the implementation of deflected motorcycle crossings and roundabout reduced critical density by 38.6% and 63.7%, respectively.
Regarding safety, more benefits are expected by using either deflected crossings or roundabout than straight crossings. The number of severe critical conflicts reduced by 87.9% with the application of a roundabout separated for main road traffic and motorcycles. This is higher than the decrease of 48.5% after the application of dedicated motorcycle lanes with deflected crossings. To determine the conflict rates per scenario, the number of severe critical conflicts was divided by total traffic simulated. Deflected crossings for motorcycles reduced severe critical conflict rate by 40% whilst it decreased by 75% with intersection improvement to a roundabout separated for main traffic and motorcycles.
With the high motorcycle demand of over 50% of traffic, implementation of dedicated motorcycle lanes at unsignalized intersections as well as urban roads in general will result into better flow of traffic. In addition, the motorcycle lanes will contribute to the general road safety in Kampala.

Urban mobility is challenged with increasing demand, while at the same time reducing emissions, without leading to an unpleasant living environment. Reducing the number of stops on the urban arterial controlled by the coordinated traffic controller can provide (part of) the solution to these challenges for urban mobility. Coordinated traffic controllers are subject to some limitations, especially regarding coordination between locally optimal signal timing plans and proactive optimization of the coordination with regards to traffic demand. These limitations where explored in this thesis, where a variable speed was proposed to be able to provide coordination between locally optimal signal timing plans and where the usage of predictions with regards to proactive optimizations was tested. A theoretical study showed no realistic potential for coordination between unequal cycle times, however theory does show significant potential of the usage of a variable speed for coordination between locally optimal signal timing plans, when coordinating in two directions. This potential of the variable speed was confirmed by using the MAXBAND model and performing a simulation study, which indicated a significant decrease in stops on the main arterial over optimizing with a fixed speed. Furthermore, the variable speed allowed for a lower network cycle time, which resulted in a decrease in delay on the side directions. Tests of demand predictions in TopTrac yielded no significant improvements of stops nor delay. In the investigated network, control decisions of the coordinated traffic controller did not correlate closely with fluctuating demand, which is needed for a prediction of the demand to produce significant improvements regarding the stops and delay in the network. Future research should focus on the variable speed, evaluating the theoretical applications in other networks and exploring the practical applications, potentially via Intelligent Speed Adaptation (ISA).

Current day routing systems use predicted travel times to calculate optimal routes. Some routing algorithms even use predicted traffic lights states to optimize these routes and to improve the expected travel time. But all these methods optimize the expected travel time and do not take reliability into account. Reliability is a major service indicator and with non-flexible departure or arrival constraints, the value of reliability can increase up to three times the value of time (Markovich, Concas, & Kolpakov, 2009). To use a measure of reliability, not the expected travel time, but the travel time distribution should be known. Since reliability is not uniquely defined, an algorithm is designed with an individual cost function, that gives users the freedom to use their own definition of reliability. Since knowing the traffic light states at intersections could improve the travel time and reliability, this should be used in the algorithm as well. Therefore the main goal of this research is: Designing an urban routing algorithm, that incorporates predicted traffic light states, where the routing is based on the probability distribution of the travel time and an individual cost function that expresses the tradeoff between travel time and reliability. For this research only urban areas with traffic lights are considered, other intersections in this network are not taken into account. The traffic lights are assumed to be traffic lights with a changing cycle time. If this algorithmworks for these traffic lights it will also work for fixed time traffic lights and most other type of traffic lights, since these have less degrees of freedom.

Fixed-time control and vehicle-actuated control are two main signaling strategies implemented at intersections for urban traffic management. The timing and structure of the controllers are usually designed optimally based on average historical demand patterns at the intersection. Under the premise of performance quality assurance, both fixed-time and vehicle-actuated controllers can accommodate a certain degree of demand fluctuations. As a matter of fact, the demand change can be considerable over the years, which could exceed their capacities in adapting such degree of demand change, and thus the signal controllers should be regularly updated to fit the latest demand. To some extent, how much demand change can be adapted by both types of the signal controllers determines how frequent should the controllers be checked and improved. However, only qualitative comparison of the capabilities in demand adaptation between fixed-time and vehicle-actuated controllers are made in most of existing literatures, according to which vehicle-actuated controllers are expected to have higher capabilities in accommodating demand changes. In this research, a quantitative analysis and comparison were made for the fixed-time and vehicle-actuated controllers at a right-turning channelized intersection under various demand conditions. Since no useful studies could be found to predict the demand changes towards a specific intersection at current phase, the extra demand that could be accommodated by vehicle-actuated controllers were investigated instead. And it is found that the vehicle-actuated controllers can serve a 19% to 204% of more demand compared with the fixed-time controllers in scenarios defined in this research, according to which the redesign frequency can be further determined for both types of controllers to maintain comparable operation performance.

The Hyperloop concept is a new method of transportation. Con side ring this, it still has a vast amount of challenges to tackle and overcome. One of these challenges is the boarding security system, on which this research is focused. The Hyperloop is a tube-based transport method. The pods in which passengers travel have to be entered via certain access points, since the tube is in near vacuum state and can not be entered everywhere along its length. To ensure security and safety of the system's users, a boarding security system is required. In this report, the aim is to create the beginnings of a design of such a boarding security system. Several already-existing transportation methods, which can be compared to the Hyperloop in one or a number of ways, were analyzed for their boarding security systems. Their boarding processes, risks and measures were noted. This was done by arranging each of the systems risks, related to boarding security, and combining these with their respective measures, costs and placement. The transportation methods which had the highest risks, also had the most and most extreme measures to combat these respective risks. The Hyperloop is a closed system. This enables it to be considered a high-risk system, mainly because emergency exits and access for help are hard to realize. Another aspect which increases risk, is the high velocity at which the Hyperloop is expected to operate. This high velocity can accelerate and multiply the resulting damage in case an accident happens. The most significant analyzed transportation method (in terms of amount of terrorist countermeasures) was the airplane. At an airport, a combination of cameras, active personnel (such as guards and camera surveillants) and extensive security checks are implemented to maximize security. To custom fit a security system to the Hyperloop, the actual properties of the Hyperloop system itself have to be determined. Therefore, a certain variation of the Hyperloop was chosen out of several to further use in this report. The chosen variation has four key features; the tube is placed above ground surface level, the pods are sized to fit about 20 passengers, the transportation system can be used without reservation and the pods enter a pressurization room (locked and entered by gates) to make it possible for travelers to enter. The risks of this specific system were determined to mostly be hijackings and bombings, this was done by analyzing terrorist attack statistics. Before determining the boarding security system's elements, limitations were set. These limitations limit (and change) the security measures, by implementing other factors that should be considered. This is an important part, since an overflow of security measures can increase overall system costs and therefore degrade user experience. These limitations were costs, time delays and differences in laws and culture per country. Costs were chosen to not be varied, since the overall security costs per ticket price are but a small portion of the expected overall ticket price (about €10 per flight per person for air travel, which will be used as a simplification). Two significant limitations are time delays and regional differences. Time delays reduce travel flow. Regional differences, like terror attack probability per nation, influence the required anti-measures. These two limitations are combined to create two versions of the boarding system. One version is automated, which costs less time but is possibly less safe. The other one is a partially automated system with manual additions, which takes up more workforce and time (e.g. by also performing checks by hand) but the re fore increases security by broadening the overall security process. The implemented system will depend on the specific region. The boarding security system consists out of the following components: - Luggage and passenger check, which includes metal detectors, x-ray scanners and possibly explosive detection devices. - A well-ordered, structure d boarding procedure which enhances the capability to maintain an overall view on what is happening and what the passengers are doing. This means a mostly guided system, initiated once the traveler enters the station facility. The guiding of the travelers is to mainly happen via the station's layout; the positioning of gates and rails, which indicate the path passengers are to follow. This makes it easier for the personnel to spot extraordinary activities. - A team of personnel to inspect the camera footage, perform checks in manual regions and operate as security guards and first-aid helpers. As one can tell, the defined boarding security system above seems to resemble that of an airport. However, a key difference is that air flights are reserved. The Hyperloop, according to the assumed system used in this report, is not. Therefore, the 3rd point of the boarding security system (well­ordered boarding procedure) is of great importance. By increasing the structure in the system, it becomes easier for the personnel to focus on their respective function which can increase efficiency.

Permitted conflicts at (vehicle-actuated) signalised intersections are widely researched, though with the main focus on the traffic safety implications, because with permitted conflicts, two or more conflicting streams at a signalised intersection receive green at the same time, and thus meet at the conflict zone, as opposed to protected conflicts. The literature pays little attention to the traffic flow efficiency effects. Although some literature introduce some of these traffic flow efficiency effects, no detailed research has been done. This Additional Graduation Work contributes to this knowledge gap by introducing the potential traffic flow efficiency effects of permitted conflicts. In a simulation study, in which the gap acceptance behaviour of the simulation model Vissim is briefly tested, it is found that permitted conflicts (i) reduce the cycle time, (ii) reduce the queue length, and (iii) reduce the delay experienced by various road users at the signalised intersection. However, this comes at the cost of reduced saturation flow. Also, it is hypothesised that there is some turning point in terms of traffic flow volumes, and the distribution of volumes per approach at which the traffic flow efficiency effects become negative. This relates to the various traffic safety conditions that must be met at the signalised intersection with permitted conflicts as well, to ensure a safe conflict handling, which include that the traffic flow volumes may not be too large. Nonetheless, the traffic flow efficiency effects, in terms of intersection throughput and capacity, queues, and travel times and delays, of implementing permitted conflicts, as opposed to implementing protected conflicts on signalised intersections, are positive, in that sense that it resulted in shorter cycle times, less delay, and shorter queues on average. For signal groups with priority, the number of stops also decreased. Although there is a risk of oversaturation, the overall conclusion is that the traffic flow inefficiency effects are positive on average. In short, this comes down to that fewer protected conflicts, equals a higher traffic safety risk, but also a more efficient traffic flow, on average, hence the title of this research.

Traffic signal controllers have been around since the late sixties of the 19th century and since then they have played an increasing role in (urban) traffic management. Over the years many different algorithms have been developed and in Dutch practice actuated control is mostly used. Actuated control and other similar approaches apply variable green times to handle demand fluctuation, which leads to a reduction of the delay for vehicles in comparison to e.g. fixed-time control, however, in actuated control it is difficult to accurately predict control decisions. This study proposes a new traffic signal control algorithm that creates a planning of control decisions based on expected vehicle arrivals. By doing so, predictability of control decisions increases, while no sacrifices need to be made regarding the optimality of the control policy. Since certain errors such as inaccurate queue discharge rates are incorporated in the planning of control decisions, a second algorithm is required that adjusts the planning of control decisions to actual traffic conditions. Using an N65 case study intersection the performance of the new traffic signal control algorithm is compared to other algorithms. Depending on the availability of vehicle arrivals and the composition of traffic flows at the intersection, the new algorithm outperforms standard Dutch actuated traffic signal control in terms of overall delay by 3.1% to 4.7%. A range of improvement possibilities is suggested to ensure a greater reduction of the delay.