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

Differentiated Road Pricing, Express Lanes and Carpools: Exploiting Heterogeneous Preferences in Policy Design

In the face of rising congestion on the nation's road system, policymakers have explored ways to reduce travel delays. One approach has been to allocate reserved lanes, called high-occupancy-vehicle (HOV) lanes, to vehicles carrying two or more people. A recent innovation is to allow solo drivers to use the HOV lanes if they pay a toll. These so-called high-occupancy-toll (HOT) lanes can be found in Los Angeles, San Diego, Houston, and Minneapolis and are under consideration in several other urban areas. In this paper, we argue that HOV and HOT lanes sacrifice efficiency by failing to price all lanes.Moreover, we show that it is possible to set prices on all lanes that improve on the efficiency of HOV and HOT policies and by catering to motorists' varying preferences, can meet the test of political acceptability.

US Highway Privatization and Heterogeneous Preferences

Abstract: We assess the welfare effects of highway privatization accounting for government’s behavior in setting the sale price, firms’ strategic behavior in setting tolls in various competitive environments, and motorists’ heterogeneous preferences for speedy and reliable travel. We conclude motorists can benefit from privatization if they are able to negotiate aggressively with a private provider to obtain tolls and service that align with their varying preferences. Surprisingly, motorists are likely to be better off negotiating with a monopolist than with duopoly providers or under public-private competition. Toll regulation may be counterproductive because it would treat motorists as homogeneous. Revised June 2009.Security Breach Costs; Financial Distress; Insurance; Resource Allocation.

Stability and Environmental Analysis of Mixed Traffic Flow – Using the Markov Probabilistic Theory

The rapid growth of CAV (Connected and Automated Vehicle) market penetration highlights the need to gain insight into the overall stability of mixed traffic flows in order to better deploy CAVs. Several studies have examined the modelling process and stability analysis of traffic flow in a mixed traffic environment without considering its inner spatial distribution. In this paper, an innovative Markov chain-based model is established for integrating the spatial distribution of mixed traffic flow in the model process of car-following behaviour. Then the linear stability analysis of the mixed traffic flow is conducted for different CAV market penetration rates, different CAV platoon strength and different cooperation efficiency between two continuous vehicles. Moreover, several simulations under open boundary conditions in multiple scenarios are performed to explicate how CAV market penetration rate, platoon strength and cooperation efficiency jointly influence the stability performance of the mixed traffic flow. The results reveal that the performance of this mixed traffic flow stability could be strengthened in these three factors. In addition to stability, an investigation of the fuel consumption and emission reduction under different market penetration rates and the platoon strength of CAVs are explored, suggesting that substantial potential fuel consumption and emission could be reduced under certain scenarios

Setting the market free: deregulation of the bus industry. 4th Smeed Memorial Lecture, 29th October 1987.

[FIRST PARAGRAPH]Though he was not himself an economist, Reuben Smeed is well known to transport economists as the chairman of a committee which, in the early sixties, examined the use of congestion charges to obtain a rational use of scarce urban road capacity. (1) The Smeed report showed that in the absence of a proper road congestion pricing system there would be an excessive use of the private car, and, by implication, a sub optimum level of use of public transport. Although, to the best of my knowledge, Reuben never turned his mind to the issues of public transport regulation, the ready acceptance of public transport regulation and subsidy as second best proxies for road pricing in the late sixties and seventies was, I believe, founded on the Smeed logic