Juan Carlos Muñoz

Moving Bottlenecks: A Theory Grounded on Experimental Observation

This paper presents the most complete picture yet of moving bottlenecks on freeways, including experimental observations and a theory. The experimental observations include the “fingerprint” of a moving bottleneck on a series of loop detectors, and a set of controlled experiments in which moving bottlenecks were artificially introduced in the traffic stream. The paper also contrasts this evidence with current theories and describes a new one that is consistent with the data. High-resolution oblique plots of loop detector data from freeway I-880 in Oakland (California) are used to analyze the aforementioned fingerprint. They clearly display the presence of the bottleneck and its evolution in time and space, including the precise location in space-time where it appeared. The data also reveal a fleeting but real change in the drivers’ car-following attitude shortly after the bottleneck’s appearance. The controlled experiments reveal that the flow downstream of the bottleneck increases with the speed of the bottleneck when the bottleneck holds back a queue—in contradiction with two previous theories (Gazis and Herman, 1992, and Newell, 1993). The new theory includes these as special cases. It treats the moving bottleneck as a boundary condition that can be integrated with kinematic wave (KW) theory and also with variants of this theory that account for multiple vehicle types and changes in driver psychology. The empirical evidence suggests that the lengths of queues upstream of moving bottlenecks and the ensuing vehicle delays can now be predicted with good accuracy.

Use of Mixed Stated and Revealed Preference Data for Crowding Valuation on Public Transport in Santiago, Chile

The valuation of comfort on public transport is presented with mixed stated preference and revealed preference data. In this case, comfort is measured mainly as the level of crowding in the vehicles (bus or train) with the use of in-vehicle passenger density (in number of passengers per square meter). The data used to value comfort include a stated preference survey in which crowding levels are presented as illustrations and revealed preference data on route choice on the subway network of Santiago, Chile. The survey data are used to estimate discrete choice models and obtain a subjective valuation of passenger density through the parameters of the utility function. Disutility for traveling in crowding conditions is assumed to be proportional to the travel time; therefore, the longer the trip, the higher the utility loss. Results indicate that passenger density has a significant effect on the utility of public transportation modes. In fact, marginal disutility of travel time in a crowded vehicle (6 passengers/m2) is twice the marginal disutility in a vehicle with a low level of crowding (1 passenger/m2).

A review of technological improvements in bus rapid transit (BRT) and buses with high level of service (BHLS)

Bus rapid transit BRT, and its European counterpart buses with high level of service BHLS, have been adopted by more than 160 cities around the world as a low cost, rapid implementation option for improved transit services. This paper summarizes some past advances of BRT and BHLS and presents some trends in vehicle guidance, propulsion technologies and information systems which are shaping the future of bus systems. We use the cities of Curitiba, Paris, Bogotá, Santiago, Istanbul, and Guangzhou to present relevant breakthroughs in bus system evolution. Thanks to the advances pioneered in these cities, BRT and BHLS became feasible alternatives to or complement metro and trams, and an integral part of integrated transit solutions, even in megacities like Mexico, Rio de Janeiro, Beijing, and New York. Evolution is ongoing; cities and providers are advancing technological components to enhance passenger experience and improve the technical, economic and environmental performance of BRT and BHLS.

THE WAR FOR THE FARE: HOW DRIVER COMPENSATION AFFECTS BUS SYSTEM PERFORMANCE

Prior to 2007, two systems of bus driver compensation coexisted in Santiago, Chile: one paid drivers per passenger transported, while the other paid a fixed wage. Per-passenger drivers engaged in “The War for the Fare,” altering their driving patterns to compete for passengers. Examining these systems on similar routes in Santiago, we observed two key findings. Compared with the fixed-wage system, the per-passenger system leads to (1) 13% shorter passenger wait times, via reduced bunching of buses and (2) 67% more accidents per kilometer driven, via more aggressive driving. We discuss implications for the design of incentives in public transit . ( JEL L92, M52, R41)

Model for the Optimal Location of Bus Stops and Its Application to a Public Transport Corridor in Santiago, Chile

The location and number of bus stops are key to the operational efficiency of the services that use them; these criteria affect commercial speed, reliability, and passenger access times. In the defining of the number of stops, a trade-off arises between reduced access time, which widens a routes coverage area, and both the operational speed of the route and the users’ in-vehicle travel time. In this study, a model for optimally locating stops was developed, and the model was applied to the Grecia Avenue public transport corridor in the city of Santiago, Chile. The proposed model uses a continuous and multiperiod approximation of corridor demand; this approximation allows for the determination of the density of stops, which minimizes the sum of operator costs and total costs to passengers. The model simultaneously solves for the optimal stop density and the headway between successive buses. The actual stop locations of the Grecia Avenue corridor were compared with the optimal locations suggested by the model, and many similarities were found.

On assigning drivers for a home-delivery system on a performance basis

Abstract Consider a firm providing home-delivery of small parcels within a short period of time. The paper proposes a method to estimate the productivity of each driver on any fictitious route using linear regressions. The method separates the trip time in terms of the time spent: with customers, driving, and all other activities. Our tests show that productivity, measured in terms of number of customers visited per hour, vary across drivers. Even more, the same driver’s productivity vary for peak and off-peak demand periods considerably. This methodology should enhance the reliability of the driver scheduling programs, since it reduces the error and bias of the productivity offered by the assigned set of drivers. It shall also improve the reliability of the delivery time promised to the customer.

Examining regulatory reform for bus operations in Latin America

Governments in Latin American cities are pursuing regulatory reforms to address the negative externalities of informal public transportation service providers. This is achieved by regulatory actions that work to consolidate many small operators competing “in the market” into fewer larger companies competing “for the market.” This reform addresses problems in the previous phase of the regulatory cycle, but requires a larger role for public authorities. The cities of Bogotá, Santiago and Mexico City took different approaches and have achieved different levels of formalization. Under these cities’ new regulatory regimes, bus companies have consolidated and public authorities now rely on renegotiation of contracts instead of open rebidding. However, industry formalization increases costs, requiring public subsidy or higher fares, and puts financial pressure on the public sector. These results imply a continued instability in the regulatory cycle; without increased public sector capacity, it is possible that large, entrenched operators and increasing costs will create a new market opening for informal service.

The impact of multi-skilling on personnel scheduling in the service sector: a retail industry case

Using personnel scheduling to reduce overstaffing and understaffing in a service industry across multiple periods is often undermined by lack of flexibility due to the exclusive use of specialized personnel. This study analyses the impacts of assigning multi-skilled personnel to different activities and its potential for improving schedule efficiency. A proposed mixed integer linear programming model determines which employees are trained to work in which activities and their assignments over a one-week planning horizon. The model results show that the lowest total-cost multi-skilled configurations are obtained in scenarios where personnel supply and demand are in equilibrium. Half of employees would continue to be specialized for just one activity while the half slated for multi-skilling would be trained in most cases for just one additional activity, even though training cost is assumed to be minimal. It is also shown that multi-skilling is best applied to employees whose contracts are highly flexible.

A continuous approximation model for locating warehouses and designing physical and timely distribution strategies for home delivery

Abstract This article proposes a methodology based on continuous approximation to address the common logistics problems of locating warehouses and designing physical distribution strategies for a delivery firm with short and immediate time windows of different urgency (e.g., 1 or 2 h). An objective function is developed that includes the principal cost factors (warehouse rental, transportation, inventory cost, and wages). The methodology was applied to the real case of a company in Santiago, Chile, generating a demand model and an optimal logistics design that produced satisfactory results in terms of optimal warehouse locations and associated costs.

When and where are limited-stop bus services justified?

ABSTRACT Although limited-stop bus services around the world have proven to benefit users and operators alike, there are few published studies on design methodologies for such services and little clarity on when or where they are best applied to a given bus corridor. This article reports on an experiment in which a design algorithm for limited-stop services in a corridor was used to optimise almost 1000 scenarios. A regression model was then calibrated to estimate the benefits of operating limited-stop bus services as a function of various attributes of the corridor. The benefits from limited-stop services increase with higher dwell times, number of trips, concentration of trips in few origin–destination pairs and critical arc load, and with lower wait time values and vehicle capacity. The analytic expression derived from the regression model provides an unprecedented tool to forecast the benefits of implementing limited-stop services.