Road safety effects of porous asphalt: a systematic review of evaluation studies

doi:10.1016/j.aap.2005.01.003

Accident Analysis & Prevention

Volume 37, Issue 3, May 2005, Pages 515-522

https://doi.org/10.1016/j.aap.2005.01.003 Get rights and content

Abstract

This paper presents a systematic review of studies that have evaluated the effects on road safety of porous asphalt. Porous asphalt is widely used on motorways in Europe, mainly in order to reduce traffic noise and increase road capacity. A meta-analysis was made of six studies, containing a total of eighteen estimates of the effect of porous asphalt on accident rates. No clear effect on road safety of porous asphalt was found. All summary estimates of effect indicated very small changes in accident rates and very few were statistically significant at conventional levels. Studies that have evaluated the effects of porous asphalt on nine different risk factors associated with accident occurrence were also reviewed. It was found that four of the risk factors were favourably influenced by porous asphalt, three were adversely influenced, and two were not influenced by porous asphalt. The net impact of these changes in risk factors on accident occurrence cannot be predicted. On the whole, the research that has been reported so far regarding road safety effects of porous asphalt is inconclusive. The studies are not of high quality and the findings are inconsistent.

Introduction

Porous asphalt is used in many European countries, mainly in order to reduce traffic noise and increase road capacity. Porous asphalt differs from ordinary dense asphalt concrete by having an open structure with approximately 20–25% air filled pores. The open structure of porous asphalt reduces traffic noise, drains water from the road surface and reduces thermal conductivity.

As part of a European research project (SILVIA = Silenda Via = Sustainable Road Surfaces for Traffic Noise Control), a systematic review has been made of studies that have evaluated the effects of porous asphalt on road safety. The objective of this paper is to present the results of that systematic review. The main questions that were asked in the review were:

1.
What are the effects on road safety of porous road surfaces?
2.
Do the effects on road safety of porous road surfaces vary according to accident severity and road surface condition?
3.
Do the effects on road safety of porous road surfaces vary across countries?
4.
How long do the effects on road safety of porous road surfaces last?

In order to answer these questions, studies that have evaluated the effects of porous asphalt on accident occurrence and on risk factors associated with accident occurrence have been reviewed (Elvik and Greibe, 2003).

Section snippets

Study retrieval

A search was made for relevant studies in the TRANSPORT literature database using the combination of “road safety” and “road surfaces” as search terms. This literature database contains all references found in TRIS, IRRD and TRANSDOC. In addition, a previous literature review (Greibe, 2000) was used as a source. A total of 16 studies that have evaluated effects on accidents of road surface treatments, and that have been published after 1990, were retrieved. Porous asphalt was not widely used

Findings of evaluation studies

The six studies that were included in the systematic review of effects on accidents are listed in Table 2. A total of 18 estimates of effect were extracted from these six studies. Details regarding the extraction of estimates of effect from each study can be found in the main report (Elvik and Greibe, 2003). All studies stated effects in terms of the accident rate ratio: $accident rate ratio = \frac{number of accidents on roads with porous asphalt / kilometres of driving on roads with porous asphalt}{number}$

Discussion and interpretation

A distinction is sometimes made between two ways of interpreting the results of research: (1) Methodological, and (2) Substantive. A methodological interpretation of research usually criticises the research by pointing out flaws in research methods. In this paper, the methodological point of view is represented by the quality assessment made of studies that have evaluated the effects on accidents of porous road surfaces. A formal quality scoring system has been used. According to this system,

References (21)

J.B. Edwards
Motorway speed in wet weather: the comparative influence of porous and conventional asphalt surfacings
J. Transport Geogr.
(2002)
R. Elvik
The importance of confounding in observational before-and-after studies of road safety measures
Accident Anal. Prevent.
(2002)
Bendtsen, H., Larsen, L.E., Greibe, P., 2002. Udvikling af støjreducerende vejbelægninger til bygader, Statusrapport...
J. Bonnot
French experiences of porous asphalt
M.C. Brailly
Porous macadam and road safety
Commandeur, J.J.F., Bijleveld, F.D., Braimaister, L.G., Janssen, S.T.M.C., 2002. De analyse van ongeval-, weg-, en...
Delanne, Y., Laganier, R., Christophe, T., Gondoni, N., Duboil, C., Begou, P.A., 1991. Skid resistance of drainage...
S. Duval et al.
Trim and fill: a simple funnel plot based method of testing and adjusting for publication bias in meta-analysis
Biometrics
(2000)
Elvik, R., Greibe, P., 2003. Safety aspects related to low noise road surfaces. Report 680. Institute of Transport...
R. Elvik et al.
Handbook of Road Safety Measures
(2004)

There are more references available in the full text version of this article.

Cited by (40)

Temporary clogging effects induced by a sustainable anti-icing hydrogel on the hydraulic conductivity and inertia coefficient of open-graded asphalt pavements
2022, Construction and Building Materials
Open-graded asphalt pavements require special winter maintenance procedures to ensure the effectiveness of anti-icing and deicing measures. A recently developed solution for this type of pavement is represented by an environmental friendly thickened bio-based salt hydrogel, which consists of a thermo-sensitive sodium chloride (NaCl) brine admixed with a gellant agent (seaweed fibers) having the ability to form a gel-like structure when hot-sprayed on a cold surface. This thin salt layer results in a long-lasting residual efficacy of the winter maintenance product and in a reduction of salt consumption, but affects the drainage capacity of the pavement. These transient clogging effects were evaluated on laboratory-made specimens through the measurement of their vertical hydraulic conductivity variations before and after the hydrogel application, using a 1-D air permeameter and a constant head water permeameter. The analyses, based on Darcy–Forchheimer model and Darcy model for lower Reynold numbers, revealed a significant short-term reduction of the hydraulic conductivity, that, anyway, tends to be almost totally restored once the critical weather event is over (after about 6 h).
Phyto-based sodium chloride hydrogel for highway winter maintenance of porous asphalt pavements
2022, Construction and Building Materials
Citation Excerpt :
Regardless of the construction technique, the enhanced effectiveness for stormwater management results in several safety and environmental benefits. These kind of pavements can minimize hydroplaning potential by improving the wet pavement frictional resistance and reduce water splash and spray, nighttime surface glare in wet conditions and tire-pavement noise [19–21]. But despite these inherent advantages, the open-graded layout and surface macro-texture of porous asphalt pavements affect their thermo-hygrometric regime at low temperatures, as well as the management of winter maintenance operations [22].
The need of the highway agencies to customize their winter maintenance operations on porous asphalt pavements prompted the authors to develop an innovative anti-icing technology based on the hot liquid spray application of a saline hydrogel. A bio-based (phyto-based) thermo-sensitive sodium chloride (NaCl) brine, that has the ability to form a gel simply by coming into contact with a very cold surface, was conceived. The increase in viscosity and the formation of a gel-like structure would make this anti-icing product able of filling the surface voids without permeating through the mixture (longer residual deicing effectiveness), while maintaining at the same time the pavement frictional resistance. In view of adopting sustainable winter maintenance strategies, this innovative blend was formulated by exploiting the thickening and gelling properties of wall-cell polysaccharides contained in seaweeds fibers. The mechanisms of gel formation were experimentally studied in laboratory, analyzing in detail the thermal and rheological properties of the salt hydrogel during the different phases of preparation, storage and application. On the basis of this characterization, a full-scale validation was carried out on an existing highway porous asphalt pavement. For this purpose, a tank truck prototype was equipped with a heating capacity tank and a customized specific spraying system.
Advances and development trends in eco-friendly pavements
2021, Journal of Road Engineering
The major contemporary in road pavement engineering is related to the creation of green and sustainable infrastructures, e.g., reduction of environmental impacts, increase in traffic safety, and transportation efficiency, etc. This review presents the recent trends in research and the technical solutions developed so far to address these challenges. After the analysis of research status in the past decades, a novel technology system of eco-friendly pavements is proposed considering two solutions, materials modification and structure improvement. The construction of an eco-friendly pavement can be achieved thanks to several different technologies ensuring permeable, noise-reducing, self-luminous, and exhaust-decomposing properties as well as apporting lower heat absorbing and enhanced anti-/de-icing characteristics. A systematic review of these technologies is presented pivoting on four main aspects: technical principle, material and structural composition, performance evaluation, and engineering application. The current trend in road engineering is combining the pavement infrastructure with various eco-friendly functions, e.g., water permeability, noise reduction, low heat absorption, exhaust gas decomposition, and anti-/de-icing. Finally, the review lists the drawbacks of the existing technologies, including high cost, single function, etc., and depicts the future developing direction and architecture of the next generation of eco-friendly pavements in which the road infrastructure should have more environmentally friendly functions than the existing technology.
Reuse of carbon fiber composite materials in porous hot mix asphalt to enhance strength and durability
2019, Case Studies in Construction Materials
Porous hot mix asphalt (PHMA) allows runoff to infiltrate through the pavement. Cured carbon fiber composite materials (CCFCM)s from aerospace production lines were ground into three size groups (Fine, Medium, and Large) and reused as reinforcement agents for PHMA in comparison to commercial synthetic fiber. The Fine CCFCMs premixed with liquid asphalt binder performed the best to reinforce PHMA in terms of indirect tensile strength and cracking resistance at both 25 °C and −10 °C. The addition of fine CCFCMs and synthetic fibers reduced the porosity by 17% and infiltration rate by up to 20%, while both fibers showed to prevent draindown of asphalt binder at an elevated temperature. The PHMA reinforced with the Fine CCFCMs performed the best in rutting resistance.
Evaluation of the benefits of open graded friction course: Case study
2018, Construction and Building Materials
Citation Excerpt :
Hernandez-Saenz et al. [13] asserted that these safety-related benefits were the main reason for using OGFC mixtures in the United States. However, some studies challenged that the safety effectiveness of OGFC was limited and inconclusive [14,15]. They claimed that the road user usually drives faster on OGFC surfaced pavements, which might result in a higher accident rate as compared to the conventional pavements.
This study evaluated the benefits of Open Graded Friction Course (OGFC) via two field projects constructed by the Nevada Department of Transportation: one project was in Elko, and the other was in Las Vegas. Each project included both the OGFC and Dense-Graded Hot Mix Asphalt (DGHMA) sections. The Elko project was located in the town area of Elko while the Las Vegas project was constructed in a rural area on I-15 interstate highway. Laboratory tests were performed to evaluate the durability, rutting, and moisture-susceptibility of OGFC mixtures. The selected test methods included the Cantabro test, Tensile Strength Ratio test, and Hamburg Wheel-Track test (HWTT). The laboratory test results showed that the Las Vegas OGFC mixture passed all the performance criteria, but the Elko Mixture failed to satisfy the HWTT criterion.
The field performance tests were conducted to assess the permeability, friction, and noise functionality over time. The selected test methods included the NCAT falling head permeameter test, locked-wheel skid trailer test, and On-Board Sound Intensity test. The field performance results demonstrated that the Las Vegas OGFC pavement exhibited benefits in permeability, friction, and noise reduction compared to the DGHMA pavement, while the Elko OGFC pavement showed comparable performance with the DGHMA pavement after 2-years of service. Finally, a cost-benefit analysis was conducted to monetize the advantages and disadvantages of OGFC pavements. As demonstrated in the economic analysis, the OGFC pavement in Las Vegas reduced the net present value of OGFC costs by 36%, while the OGFC pavement in Elko increased the net present value of costs by 86%. This indicates that the implementation of OGFC is cost-effective in rural highways but impractical in urban or town areas. High speed traffic is generally needed to help keep the interconnected voids of an OGFC pavement from becoming clogged over time. As a result of the reduced speed on the Elko project, the permeability functionality was lost after one year and the noise reduction benefit was lost after thirty two months.
Study of the porous asphalt performance with cellulosic fibres
2017, Construction and Building Materials
Citation Excerpt :
The porous asphalt can be applied both in conventional pavements with impermeable base layer, and also in permeable pavements with a fully constituted structure by porous layers [10–13]. In addition to the effects associated to surface runoff improvement, the application of these mixtures allows the decrease of the urban heat island effect, reduce the tires noise, the surface runoff and, consequently, the spray effect and aquaplaning, leading to a safer driving [14–16]. Noise reduction is also improved by the increase of porous asphalt air voids content with the help of the aggregates optimized sieve line [17,18].
The porous asphalt (PA) use in road pavements surface layers is one of the most common solutions worldwide to address the climate changes impact like heavy rain. The aim of this study is to evaluate the performance of these mixtures with the cellulosic fibres addition, known for their adherence capacity between the aggregates and the binder. These will help to prevent the binder loss by drainage, which is one of the main problems of porous asphalt, since the fine aggregates content is reduced. Comparing to the conventional porous asphalt the cellulosic fibres addition improved performance to permanent deformation.

View all citing articles on Scopus

View full text

Road safety effects of porous asphalt: a systematic review of evaluation studies

Abstract

Introduction

Section snippets

Study retrieval

Findings of evaluation studies

Discussion and interpretation

J. Transport Geogr.

Accident Anal. Prevent.

French experiences of porous asphalt

Porous macadam and road safety

Trim and fill: a simple funnel plot based method of testing and adjusting for publication bias in meta-analysis

Biometrics

Handbook of Road Safety Measures