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Impact of Speed Limits and Road Characteristics on Free-Flow Speed in Urban Areas
KTH, School of Architecture and the Built Environment (ABE), Transport Science.ORCID iD: 0000-0002-7080-5176
KTH, School of Architecture and the Built Environment (ABE), Transport Science.
2016 (English)In: Journal of transportation engineering, ISSN 0733-947X, E-ISSN 1943-5436, Vol. 142, no 2, 04015039Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

The paper documents studies of posted speed limit (PSL) changes on the free-flow speed on urban roads. Before and after field measurements were conducted, changing the existing PSL from 50 to 40 or 60 km/h. The analysis was conducted on the mean free-flow speed difference and speed variability. The data collected were also used for multiple regression analysis, including PSL changes and selected self-explaining road characteristics. The results showed that a decreased PSL caused a small (1.6 km/h) but significant reduction in the mean free-flow speed and speed variance, which might lead to a 10% reduction of severe injury accidents. Furthermore, the PSL reduction had a larger impact on faster drivers and higher road network classes. Conversely, an increased PSL resulted in a 2.6 km/h increase in the mean free-flow speed but no change on speed variability. The regression results indicated that the free-flow speed was heavily influenced by road characteristics, such as carriageway width, road environments, and the presence of on-street parking and sidewalks. Arterial roads presented the largest impact. The PSL had a relatively small impact.

Place, publisher, year, edition, pages
2016. Vol. 142, no 2, 04015039
Keyword [en]
Posted speed limit, Urban roads, Free-flow speed, Road characteristics and traffic safety
National Category
Civil Engineering
Identifiers
URN: urn:nbn:se:kth:diva-182774DOI: 10.1061/(ASCE)TE.1943-5436.0000800ISI: 000368838900001Scopus ID: 2-s2.0-84955467606OAI: oai:DiVA.org:kth-182774DiVA: diva2:906082
Note

QC 20160223

Available from: 2016-02-23 Created: 2016-02-23 Last updated: 2016-11-09Bibliographically approved
In thesis
1. Advancing Traffic Safety: An evaluation of speed limits, vehicle-bicycle interactions, and I2V systems
Open this publication in new window or tab >>Advancing Traffic Safety: An evaluation of speed limits, vehicle-bicycle interactions, and I2V systems
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Since the introduction of motor vehicles, the number of fatalities and accidents has been a concern for society.The number of fatalities on roads is amongst the most common causes of mortality worldwide (WHO, 2015).Even in industrialized countries the number of fatalities remains unacceptable. Therefore, in the last decades, anumber of approaches have emerged to support and boost traffic safety towards a system free from fatalities andserious impairment outcomes. ‘Sustainable Safety’ and ‘Vision Zero’ are well-known examples aiming to avoidfatalities within the traffic system and reduce injury severity when a traffic accident is inevitable. However, thenumber of fatalities and seriously injured accidents are still relatively high. More specifically, vulnerable roadusers remain involved in fatal and serious accidents even in industrialized countries. Therefore, further advancesin traffic safety studies are needed. This thesis aims at evaluating the impact of road characteristics, traffic rulesand information provision towards a safer traffic system. The thesis is composed of five scientific papers whichsummarizes the main contributions of this work.

Place, publisher, year, edition, pages
Stockholm: KTH, 2016. 20 p.
Series
TRITA-TSC-PHD, 16-008
Keyword
Traffic safety, urban roads, posted speed limits, road characteristics, free-flow speed, time headway, vehicle-bicycle interactions, logit model, yielding probability, cooperative systems and warning messages.
National Category
Transport Systems and Logistics
Research subject
Transport Science
Identifiers
urn:nbn:se:kth:diva-195640 (URN)978-91-87353-94-9 (ISBN)
Public defence
2016-12-16, Kollegiesalen, Brinellvägen 8, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20161109

Available from: 2016-11-09 Created: 2016-11-07 Last updated: 2016-11-10Bibliographically approved

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