SEEK: Salford Environment for Expertise and Knowledge

Journal Article (Refereed)
June 2013

Effect of road narrowing on junction capacity using microsimulation

Yousif, S & Alterawi, M & Henson, R R 2013, 'Effect of road narrowing on junction capacity using microsimulation', Journal of Transportation Engineering, 139(6), pp.574-584.


Traffic calming measures have been widely used in urban areas with the aim sometimes of reducing vehicles flow rates but mainly to reduce speed and hence the number and severity of traffic accidents. The one-way priority working road narrowing (throttle) is a widely used traffic calming technique. However, installation of such a measure close to a junction can severely affect the operation and level of service, especially for the major road movements. There is a lack of research, guidance and design standards to inform the effective deployment of such a measure.

This paper starts by providing a summary of the terms and standards used in practice for traffic calming measures, mainly focusing on the use of throttles. The paper aims to investigate the relationship between throttle spacing (X) from a priority junction and the "major to major movement" driver's delay for different flow levels using the Paramics micro-simulation model. The model was calibrated and validated with field data taken from a selected site within Greater Manchester for two separate days using camcorders. Cooperative behavior between drivers (i.e. those with priority who gave way to others) was noticed and analyzed accordingly. Different scenarios were used to test the effects on delays and queues for various parameters including throttle spacing (X), major arms flow level and reversing the direction of priority.

The findings show that there is a direct relationship between throttle spacing (X) and the level of delay for traffic on the major arms of the junction. It is also shown that for a minor arm two-way flow level of up to 500 veh/hr, the throttle spacing should be at least 30 meters. Once the flow level reaches 700 veh/hr, the spacing should be at least 50 meters while for flow levels of 800 veh/hr, the spacing should be at least 100 meters.  Alternatively, consideration should be given to reversing the priority given to traffic by using MJTP operation (MaJor arm Traffic has Priority) rather than MNTP (MiNor arm Traffic has Priority) if less throttle sacing (X) is required, to minimize delays to traffic on the major arms.










This work considers a case study from Manchester to demonstrate how traffic calming measures operate in an urban environment. Data has been collected using camcorders and a software which is widely used in industry (i.e. PARAMICS) has been modified to test options and scenarios to improve the operation of such locations close to busy junctions. The importance of this paper is mainly to suggest better ways of designing such traffic calming measures to help alleviate congestion at such sites and hence improve safety.

This paper received some positive comments from the Reviewers and was approved within an extra ordinary short time (i.e. submitted on 31/7/2013 and approval date was 12/12/2012).

Journal Impact factor for Transportation Engineering – ASCE = 0.5

Number of external citations = newly published (June 2013) 


SEEK Members

External Authors

Mohammed Alterawi

Ralph R Henson

Publication Details

Journal Name
Journal of Transportation Engineering