Evaluation of In-Use Fuel Economy and On-Board Emissions for Hybrid and Regular CyRide Transit Buses, October 2012

The objective of this project was to evaluate the in-use fuel economy and emission differences between hybrid-electric and conventional transit buses for the Ames, Iowa transit authority, CyRide. These CyRide buses were deployed in the fall of 2010. Fuel economy was compared for the hybrid and control buses. Several older bus types were also available and were included in the analysis. Hybrid buses had the highest fuel economy for all time periods for all bus types. Hybrid buses had a fuel economy that was 11.8 percent higher than control buses overall, 12.2 percent higher than buses with model years 2007 and newer, 23.4 percent higher than model years 2004 through 2006, 10.2 percent higher than model years 1998 through 2003, 38.1 percent higher than model years 1994 through 1997, 36.8 percent higher than model years 1991 through 1993, and 36.8 percent higher for model years pre-1991. On-road emissions were also compared for three of the hybrid buses and two control buses using a portable emissions monitor. On-average, carbon dioxide, carbon monoxide, and hybrid carbon emissions were much higher for the control buses than for the hybrid buses. However, on average nitrogen oxide emissions were higher for the hybrid buses

Diesel Buses, Oil Prices and Premature Deaths from Particulate Matter: Understanding the Connections, Exploring Solutions

In 2000 the Environmental and Energy Study Institute hosted a briefing to discuss the complex issues surrounding diesel buses and alternative-fuel buses. In particular, the panelists addressed the environmental, public health, and economic costs associated with diesel bus emissions and discussed both the costs and benefits of alternative-fuel buses

No-boarding buses: Synchronisation for efficiency

We investigate a no-boarding policy in a system of $N$ buses serving $M$ bus stops in a loop, which is an entrainment mechanism to keep buses synchronised in a reasonably staggered configuration. Buses always allow alighting, but would disallow boarding if certain criteria are met. For an analytically tractable theory, buses move with the same natural speed (applicable to programmable self-driving buses), where the average waiting time experienced by passengers waiting at the bus stop for a bus to arrive can be calculated. The analytical results show that a no-boarding policy can dramatically reduce the average waiting time, as compared to the usual situation without the no-boarding policy. Subsequently, we carry out simulations to verify these theoretical analyses, also extending the simulations to typical human-driven buses with different natural speeds based on real data. Finally, a simple general adaptive algorithm is implemented to dynamically determine when to implement no-boarding in a simulation for a real university shuttle bus service.Comment: 49 pages, 9 figures. Video available here: https://www.youtube.com/watch?v=SBNqvTr1Aj

Electric Buses for the NFTA

This brief discusses many reasons that the NFTA should invest in using electric buses. After explaining the differences in bus technologies, it details numerous environmental, public health, and economic benefits of electric buses. The brief closes with case studies to show how other cities and counties across the world are beginning to use electric buses

Cooling Global Warming Through Transit

For generations, cars have been cool because they are perceived to correlate to independence and wealth. People’s attachment to their cars is one of the most cited examples of why government doesn’t want to invest in mass transit. Accompanying this ideology is an underlying fear and distaste for buses. Recently, Cleveland purposely avoided such a stigma in naming its new bus line “The Health Line” and referring to it always as rapid transit. Yet, providing “cool” features to buses, like making them hybrid or dressing them up like quaint trolleys, has been largely unsuccessful in overhauling the image of buses. Buses aren’t cool. Yet

Jamming transition in a homogeneous one-dimensional system: the Bus Route Model

We present a driven diffusive model which we call the Bus Route Model. The model is defined on a one-dimensional lattice, with each lattice site having two binary variables, one of which is conserved (``buses'') and one of which is non-conserved (``passengers''). The buses are driven in a preferred direction and are slowed down by the presence of passengers who arrive with rate lambda. We study the model by simulation, heuristic argument and a mean-field theory. All these approaches provide strong evidence of a transition between an inhomogeneous ``jammed'' phase (where the buses bunch together) and a homogeneous phase as the bus density is increased. However, we argue that a strict phase transition is present only in the limit lambda -> 0. For small lambda, we argue that the transition is replaced by an abrupt crossover which is exponentially sharp in 1/lambda. We also study the coarsening of gaps between buses in the jammed regime. An alternative interpretation of the model is given in which the spaces between ``buses'' and the buses themselves are interchanged. This describes a system of particles whose mobility decreases the longer they have been stationary and could provide a model for, say, the flow of a gelling or sticky material along a pipe.Comment: 17 pages Revtex, 20 figures, submitted to Phys. Rev.

A three-dimensional macroscopic fundamental diagram for mixed bi-modal urban networks

Recent research has studied the existence and the properties of a macroscopic fundamental diagram (MFD) for large urban networks. The MFD should not be universally expected as high scatter or hysteresis might appear for some type of networks, like heterogeneous networks or freeways. In this paper, we investigate if aggregated relationships can describe the performance of urban bi-modal networks with buses and cars sharing the same road infrastructure and identify how this performance is influenced by the interactions between modes and the effect of bus stops. Based on simulation data, we develop a three-dimensional vehicle MFD (3D-vMFD) relating the accumulation of cars and buses, and the total circulating vehicle flow in the network. This relation experiences low scatter and can be approximated by an exponential-family function. We also propose a parsimonious model to estimate a three-dimensional passenger MFD (3D-pMFD), which provides a different perspective of the flow characteristics in bi-modal networks, by considering that buses carry more passengers. We also show that a constant Bus-Car Unit (BCU) equivalent value cannot describe the influence of buses in the system as congestion develops. We then integrate a partitioning algorithm to cluster the network into a small number of regions with similar mode composition and level of congestion. Our results show that partitioning unveils important traffic properties of flow heterogeneity in the studied network. Interactions between buses and cars are different in the partitioned regions due to higher density of buses. Building on these results, various traffic management strategies in bi-modal multi-region urban networks can then be integrated, such as redistribution of urban space among different modes, perimeter signal control with preferential treatment of buses and bus priority

Operating Power Grids with Few Flow Control Buses

Future power grids will offer enhanced controllability due to the increased availability of power flow control units (FACTS). As the installation of control units in the grid is an expensive investment, we are interested in using few controllers to achieve high controllability. In particular, two questions arise: How many flow control buses are necessary to obtain globally optimal power flows? And if fewer flow control buses are available, what can we achieve with them? Using steady state IEEE benchmark data sets, we explore experimentally that already a small number of controllers placed at certain grid buses suffices to achieve globally optimal power flows. We present a graph-theoretic explanation for this behavior. To answer the second question we perform a set of experiments that explore the existence and costs of feasible power flow solutions at increased loads with respect to the number of flow control buses in the grid. We observe that adding a small number of flow control buses reduces the flow costs and extends the existence of feasible solutions at increased load.Comment: extended version of an ACM e-Energy 2015 poster/workshop pape