Traffic Operations and Management

Traffic Flow on Signalized Streets

Daganzo, Carlos F.
Lehe, Lewis J.
2016

This paper considers a signalized street of uniform width and blocks of various lengths. Its signals are pretimed in an arbitrary pattern, and traffic on it behaves as per the kinematic-wave/variational theory with a triangular fundamental diagram. It is shown that the long run average flow on the street when the number of cars on the street (i.e. the street’s density) is held constant is given by the solution of a linear program (LP) with a finite number of variables and constraints. This defines a point on the street’s macroscopic fundamental diagram. For the homogeneous special case...

Automated System for Preventing Vehicle Bunching

Saloner, Dylan
Daganzo, Carlos F.
2015

The present invention contemplates a distributed automatic control system for preventing the vehicle bunching. Information of vehicle locations is automatically detected and used to determine the positions and velocities of vehicles along a route. Vehicles pass predetermined points, such as stations, along the route. Information about whether the vehicle skipped the station, arrived at the station, or departed from the station, is automatically calculated based on the position and velocity information. This information is distributed among the vehicles that belong to the same route....

Traffic Flow on Pedestrianized Streets

Daganzo, Carlos F.
Knoop, V. L.
2016

Giving pedestrians priority to cross a street enhances pedestrian life, especially if crosswalks are closely spaced. Explored here is the effect of this management decision on car traffic. Since queuing theory suggests that for a given pedestrian flux the closer the crosswalk spacing the lower the effect of pedestrians on cars, scenarios where pedestrians can cross anywhere should be best for both cars and pedestrians. This is the kind of pedestrianization studied. Analytic formulas are proposed for a pedestrianized street’s capacity, free-flow speed and macroscopic fundamental diagram. Of...

Zone Pricing in Theory and Practice

Daganzo, Carlos F.
Lehe, Lewis J.
2016

Amid growing recognition of the costs of downtown congestion and scarcity of revenues for new roads, congestion pricing for downtown areas -- a practice we call “zone pricing” -- has begun to receive wide attention. From 1975-2003, zone pricing failed to spread beyond Singapore, but by the 2000’s technological advances had made the practice more widely practical. Now London, Stockholm, Milan and Gothenburg have schemes of their own, and zone pricing is on the agenda in many world cities. The research summarized in this report has sought to advance practical knowledge of zone pricing in...

Coordinating Transit Transfers in Real Time

Anderson, Paul
Daganzo, Carlos F.
2017

Transfers are a major source of travel time variability for transit passengers. Coordinating transfers between transit routes in real time can reduce passenger waiting times and travel time variability, but these benefits need to be contrasted with the delays to on-board and downstream passengers. This paper develops a dynamic holding strategy for transfer coordination where the decision to hold depends on real-time estimates of bus arrivals and passenger numbers and the uncertainty in these estimates. The strategy is then optimized based on the estimates. It is found that all the...

The Effect of Pedestrian Crossings on Traffic Flow

Knoop, V. L.
Daganzo, Carlos F.
2017

In urban areas and especially in inner cities, pedestrians crossing the road considerably influence the road traffic flow. For political (environmental) reasons, priority could be given to pedestrians. This paper studies to which extent crossing pedestrians influence the road traffic capacity. Several distances between pedestrian crossings are considered, and moreover, a non-constant intercrosswalk spacing is considered. The focus is on the distance between pedestrian crosswalks. Both effects are quantified. The results in this paper can be used to optimize the effects of giving...

Adaptive Offsets for Signalized Streets

Daganzo, Carlos F.
Lehe, Lewis J.
Argote-Cabanero, Juan
2017

This paper shows that severe congestion on streets controlled by traffic signals can be reduced by dynamically adapting the signal offsets to the prevailing density with a simple rule that keeps the signals’ green-red ratios invariant. Invariant ratios reduce a control policy’s impact on the crossing streets, so a policy can be optimized and evaluated by focusing on the street itself without the confounding factors present in networks. Designed for heavy traffic with spillovers, the proposed policies are adaptive and need little data - they only require average traffic density readings and...

The Effect of Crosswalks on Traffic Flow

Knoop,Victor L.
Daganzo, Carlos F.
2018

In urban areas and especially in inner cities, pedestrians crossing the road considerably influence the road traffic flow. For political reasons, priority could be given to pedestrians. A larger number of crossings reduces the pedestrian load per crossing and facilitates both the pedestrian flow and the car flow; the ultimate case is a “cross anywhere” scenario. Earlier work shows that the road capacity decreases with the square of the pedestrian crossing time, hence a short crossing time is desired. Crosswalks can ensure pedestrians cross orthogonally, and thus quickly, and can thereby...

Adaptive Offsets for Signalized Streets

Daganzo, Carlos F.
Lehe, Lewis J.
2018

This paper shows that severe congestion on streets controlled by traffic signals can be reduced by dynamically adapting the signal offsets to the prevailing density with a simple rule that keeps the signals’ green-red ratios invariant. Invariant ratios reduce a control policy’s impact on the crossing streets, so a policy can be optimized and evaluated by focusing on the street itself without the confounding factors present in networks. Designed for heavy traffic with spillovers, the proposed policies are adaptive and need little data – they only require average traffic density readings and...

Effect of Transit Signal Priority on Bus Service Reliability

Anderson, Paul
Daganzo, Carlos F.
2019

As every user knows buses tend to bunch. To alleviate this problem, transit agencies introduce slack into their schedules and then hold buses back to schedule at pre-established control points along their routes. Unfortunately, this practice retards buses and only works with low frequency systems; i.e., when the headways are long. For higher frequency systems, which effectively operate without a schedule, headway-based control strategies show promise but unfortunately, they also retard buses. To alleviate bus retardation in all its forms, transit signal priority (TSP) is commonly used....