Increasing the capacity of signalized intersections with separate left turn phases

All authors:
Xuan, Y., Daganzo, C.F., Cassidy, M.J.
Host organisation: CoE Berkeley, USA
Publication year: 2011
Published in:
Transportation Research Part B: Methodological, 2011 (in press)
Research theme: Management and Control
traffic signal capacity, pre-signals, left turn phases
Research article
A separate turn phase is often used on the approach leg to an intersection with heavy left turns. This wastes capacity on the approach because some of its lanes cannot discharge during its green phases. The paper shows that the problem can be eliminated by reorganizing traffic on all the lanes upstream of an intersection using a mid-block pre-signal. If drivers behave deterministically, the capacity that can be achieved is the same as if there were no left turns. However, if the reorganization is too drastic, it may be counterintuitive to drivers. This can be remedied by reorganizing traffic on just some of the available lanes. It is shown that such partial reorganization still increases capacity significantly, even if drivers behave randomly and only one lane is reorganized. The paper shows how to optimize the design of a pre-signal system for a generic intersection. It also identifies both, the potential benefits of the proposed system for a broad class of intersections, and the domain of application where the benefits are most significant.
October 2019
Upcoming Events
Mo Tu We Th Fr Sa Su
v40    1 2 3 4 5 6
v41  7 8 9 10 11 12 13
v42  14 15 16 17 18 19 20
v43  21 22 23 24 25 26 27
v44  28 29 30 31      



The current Call is mainly directed to sub-Saharan university-based researchers with expertise on sustainable and equitable mobility and access in sub-Saharan African cities, and/or previously engaged in transport-related research, and strongly interested in carrying out interdisciplinary research on issues related to sustainable and equitable mobility and access,

Call open until 2019-10-15


The VREF invites PhD students and researchers in early stages of their career to apply for a Study Visit Grant to be supported with up to SEK 30 000.

Invitation open until 2019-10-31

Blog! Blog! Blog!

Global Mobility Research

This Meeting of the Minds' blog monthly releases interviews of global transportation researchers from the VREF's Future Urban Transport Program Network.


This CityFix series, produced by the WRI (World Ressources Institute) Ross Center for Sustainable Cities and supported by the VREF, discusses walking and cycling in cities with a special focus on low- and middle-income countries.

Each year the Håkan Frisinger Foundation for Transportation Research awards a scholarship to a prominent researcher.


About VREF

The Volvo Research and Educational Foundations (VREF) inspires, initiates and supports research and educational activities through the Future Urban Transport Programme - How to deal with the complexity of urban transport (FUT). 

Our Vision: Sustainable transport for equitable access in urban areas

Read more

© Copyright VREF