Design and Preliminary Testing of Demand-Responsive Transverse Rumble Strips

Transverse rumble strips are common practice to alert drivers by engaging their auditory and tactile senses in addition to visual senses by traffic signals. However, continuous exposure to noise and vibration by transverse rumble strips often results in diminished effectiveness and erratic behaviors, leading to additional safety challenges. In response, demand-responsive transverse rumble strips were developed as traffic safety countermeasures that reduce unnecessary noise and vibration associated with transverse rumble strips by incorporating active control of the rumble strips. Rather than staying static, demand-responsive transverse rumble strips are activated based on the presence of pedestrians, at predesignated times, or in response to abrupt changes in traffic flow. To evaluate the effectiveness of demand-responsive transverse rumble strips, the research team assessed noise and vibration data, both inside the vehicles and on the roadside, for various types of vehicles traveling at different speeds. The test data indicate that demand-responsive transverse rumble strips produced noticeable in-vehicle noise and vibration that could alert drivers to downstream events. Furthermore, demand-responsive transverse rumble strips generated sufficient noise to alert roadside pedestrians to vehicle presence but at low enough level to be considered as acceptable for a residential neighborhood use. Accordingly, demand-responsive transverse rumble strips could address the challenges that static transverse rumble strips face, by providing a design with relatively limited noise while enhancing safety

Dynamic User Equilibrium (DUE)

The quantitative analysis of road network traffic performed through static assignment models yields the transport demand-supply equilibrium under the assumption of within-day stationarity. This implies that the relevant variables of the system (i.e. user flows, travel times, costs) are assumed to be constant over time within the reference period. Although static assignment models satisfactorily reproduce congestion effects on traffic flow and cost patterns, they do not allow to represent the variation over time of the demand flows (i.e. around the rush hour) and of the network performances (i.e. in presence of time varying tolls, lane usage, signal plans, link usage permission); most importantly, they cannot reproduce some important dynamic phenomena, such as the formation and dispersion of vehicle queues due to the temporary over-saturation of road sections, and the spillback, that is queues propagation towards upstream roads

An Integrated Pipeline Architecture for Modeling Urban Land Use, Travel Demand, and Traffic Assignment

Integrating land use, travel demand, and traffic models represents a gold standard for regional planning, but is rarely achieved in a meaningful way, especially at the scale of disaggregate data. In this report, we present a new pipeline architecture for integrated modeling of urban land use, travel demand, and traffic assignment. Our land use model, UrbanSim, is an open-source microsimulation platform used by metropolitan planning organizations worldwide for modeling the growth and development of cities over long (~30 year) time horizons. UrbanSim is particularly powerful as a scenario analysis tool, enabling planners to compare and contrast the impacts of different policy decisions on long term land use forecasts in a statistically rigorous way. Our travel demand model, ActivitySim, is an agent-based modeling platform that produces synthetic origin--destination travel demand data. Finally, we use a static user equilibrium traffic assignment model based on the Frank-Wolfe algorithm to assign vehicles to specific network paths to make trips between origins and destinations. This traffic assignment model runs in a high-performance computing environment. The resulting congested travel time data can then be fed back into UrbanSim and ActivitySim for the next model run. This technical report introduces this research area, describes this project's achievements so far in developing this integrated pipeline, and presents an upcoming research agenda

Freeway Origin Destination Matrices: Not as Simple as They Seem

Travel demand can be elegantly represented using an Origin-Destination (OD) matrix. The link counts observed on the network are produced by the underlying travel demand. One could use these counts to reconstruct the OD matrix. An offline approach to estimate a static OD matrix over the peak period for freeway sections using these counts is proposed in this research. Almost all the offline methods use linear models to approximate the relationship between the on-ramp and off-ramp counts. Previous work indicates that the use of a traffic flow model embedded in a search routine performs better than these linear models. In this research that approach is enhanced using a microscopic traffic simulator, AIMSUN, and a gradient based optimization routine, MINOS, interfaced to estimate an OD matrix. This approach is an application of the Prediction Error Minimization (PEM) method. The problem is non-linear and non-smooth, and the optimization routine finds multiple local minima, but cannot guarantee a global minima. However, with a number of starting seed matrices, an OD matrix with a good fit in terms of reproducing traffic counts can be estimated. The dominance of the mainline counts in the OD estimation and an identifiability issue is indicated from the experiments. The quality of the estimates improves as the specification error, introduced due to the discrepancy between the traffic flow model and the real world process that generates the on-ramp and off-ramp counts, reduces.travel demand, OD estimation, simulation, optimization

An example of traffic-accomodating application

The traffic generated by multimedia applications presents a great amount of burstiness, which can hardly be described by a static set of traffic parameters. The dynamic and efficient usage of the resources is one of the fundamental aspects of multimedia networks: the traffic specification should first reflect the real traffic demand, but optimise, at the same time, the resources requested. This paper presents an example of application able to accommodate its traffic to managing QoS dynamically. The paper is focused on the technique used to implement the Dynamic Reallocation Scheme (RVBR) taking into account problems deriving from delay during the reallocation phase

A Model for Dynamic QoS Negotiation Applied to an MPEG4 Applications

The traffic generated by multimedia applications presents a great amount of burstiness, which can hardly be described by a static set of traffic parameters. The dynamic and efficient usage of the resources is one of the fundamental aspects of multimedia networks: the traffic specification should first reflect the real traffic demand, but optimise, at the same time, the resources requested. This chapter presents: a model for dynamically renegotiating the traffic specification (RVBR), how this can be integrated with the traffic reservation mechanism RSVP, and an example of application able to accommodate its traffic to managing QoS dynamically. The remaining of this chapter is focused on the technique used to implement RVBR) taking into account problems deriving from delay during the renegotiation phase and on the performance of the application with MPEG4 traffic

Logical topology design for IP rerouting: ASONs versus static OTNs

IP-based backbone networks are gradually moving to a network model consisting of high-speed routers that are flexibly interconnected by a mesh of light paths set up by an optical transport network that consists of wavelength division multiplexing (WDM) links and optical cross-connects. In such a model, the generalized MPLS protocol suite could provide the IP centric control plane component that will be used to deliver rapid and dynamic circuit provisioning of end-to-end optical light paths between the routers. This is called an automatic switched optical (transport) network (ASON). An ASON enables reconfiguration of the logical IP topology by setting up and tearing down light paths. This allows to up- or downgrade link capacities during a router failure to the capacities needed by the new routing of the affected traffic. Such survivability against (single) IP router failures is cost-effective, as capacity to the IP layer can be provided flexibly when necessary. We present and investigate a logical topology optimization problem that minimizes the total amount or cost of the needed resources (interfaces, wavelengths, WDM line-systems, amplifiers, etc.) in both the IP and the optical layer. A novel optimization aspect in this problem is the possibility, as a result of the ASON, to reuse the physical resources (like interface cards and WDM line-systems) over the different network states (the failure-free and all the router failure scenarios). We devised a simple optimization strategy to investigate the cost of the ASON approach and compare it with other schemes that survive single router failures

APPLICATION OF FUZZY LOGIC TO TRAFFIC SIGNAL CONTROL UNDER MIXED TRAFFIC CONDITIONS

Traffic signal control is commonly used at road intersections to minimise vehicular delay. Fixed time control shows good results in conditions where there is a little fluctuation in traffic demand, however in time-varying traffic fixed time control becomes inflexible and inefficient. This may produce traffic congestion and lead to increased delays and air pollution. Demand responsive traffic signal control must be introduced to overcome these problems. However, all the available demand responsive traffic signal control methods such as Vehicle Actuated Controller (VAC), Traffic Optimisation Logic (TOL), Microprocessor Optimised Vehicle Actuation (MOVA) and Fuzzy Logic Traffic Signal Controllers (FLTSC) have been developed for non-mixed traffic conditions, considering only motor vehicles move in clearly defined lanes, neglecting motorcycles. These demand responsive traffic signal controls are not appropriate for the mixed traffic conditions of developing countries such as Indonesia, where the traffic streams consist of different types of vehicle with a wide variation in their static, dynamic and operating characteristics, and with a particularly high proportion (30% - 70%) of motorcycles. Also there is lack of lane discipline. This thesis describes the design and evaluation of an adaptive traffic signal controller based on fuzzy logic for an isolated four-way intersection with specific reference to mixed traffic in developing countries, including a high proportion of motorcycles. Four proposed controllers have been developed for different schemes. The controllers were designed to be responsive to real time traffic demands. The study identifies two traffic parameters as appropriate as input data for an adaptive traffic signal controller under mixed traffic conditions such as the proposed FLTSC: the average occupancy rate (%) and maximum queue length (metres). The literature study suggest that this data should be collected using advances video image processing. The proposed FLTSC uses maximum queue lengths and average occupancy rates collected during the previous cycle to estimate the number of seconds of green time required by each set of signal groups during the next cycle. The effectiveness of the proposed FLTSC was analysed using the microscopic traffic simulation model VISSIM. Prior to doing so, the VISSIM model was calibrated and validated. From the validation process it was apparent that the VISSIM model could be adapted to simulate mixed traffic conditions by use of the Packet approach. In this approach, motorcycles are modelled as a group of motorcycles. The performance of the proposed FLTSC was contrasted with a Fixed Time Controller (FTC) for different case studies on a simulated four-way intersection. The FTC is represented by the calculation as suggested in the Indonesian Highway Capacity Manual. Separate analysis using TRANSYT show that this is a valid assumption to make. The simulation results show that the proposed FLTSC is generally better than the FTC in terms of the average delay of vehicles at an intersection, especially under time-varying traffic. Further analysis was carried out to compare the performance of the proposed FLTSC against a Vehicle Actuated Controller (VAC) for different traffic conditions on a simulated four- way intersection, East-West and North-South without turning movements. In order to analyse the performance of VAC, a refined VISSIM model was developed. This used the latest version of the VISSIM software and allowed individual vehicles (and particularly motorcycles) to be modelled in mixed traffic. The phase extension time is one of the most critical parameters to affect the overall performance of VAC (Bullen, 1989). To provide a fair comparison of the performance between the proposed FLTSC and the VAC, an investigation was carried out to find the most appropriate extension time for the VAC that was suitable for mixed traffic. The effect of motorcycles to the performance of the VAC was also investigated. Two schemes were carried out to observe it, namely: Scheme 1 where detector detects all vehicle types (DfT, 2006) and Scheme 2 where detector detects all vehicle types, apart from motorcycles. The simulation results show that the VAC System D (DfT, 2006) using an extension time of 1.2 seconds and the VAC Extension Principle (Kell and Fullerton, 1991) with a detector position of 30 metres and extension time of 3.0 seconds produced better performance than the other extension times tested for both schemes in terms of the average delay of vehicles. This is slightly shorter than current practice in developed countries. The simulation results indicate that the performance of the VACs with scheme 1 is generally worse than with scheme 2. The performance of the VACs with scheme 1 against scheme 2 tended to reduce significantly as the percentage of motorcycles in traffic increased. The study compares the effectiveness of FTC, VAC Extension Principle (VAC-EP), VAC System D (VAC-SD) and proposed FLTSC in various traffic conditions. The simulation results indicate that the average delay of the proposed FLTSC is close to the average delay of the FTC when used in cases with constant traffic flows but sometimes worse. However, in cases of time-varying traffic the proposed FLTSC is superior to the FTC. When comparing the simulation results of the proposed FLTSC, VAC-SD and VAC-EP, again the proposed FLTSC does not improve average delay, when traffic flows constant but produces better results in cases of time-varying traffic