INTRODUCTION

Porous asphalt pavements with stone reservoirs are a multifunctional, low impact
development technology that integrate ecological and environmental goals for a site with
land development goals, reducing the net environmental impact for a project. Not only do
they provide a strong pavement surface for parking, walkways, trails, and roadways, they
are designed to manage and treat stormwater runoff. With proper design and installation,
porous asphalt pavements can provide a costeffective solution for stormwater management
in an environmentally friendly way. As a result, they are recognized as a best practice by the
U.S. Environmental Protection Agency (U.S. EPA) and many state agencies (New Jersey
Department of Environmental Protection, 2009; Pennsylvania Department of Environmental
Protection, 2006; U.S. EPA, n.d.).

Figure 1
Unlike conventional pavements, porous asphalt pavements (Figure 1) are typically built
over an uncompacted subgrade to maximize infiltration through the soil. Above the
uncompacted subgrade is a geotextile fabric, which prevents the migration of fines from the
subgrade into the stone recharge bed while still allowing for water to pass through the next
layer is a stone reservoir consisting of uniformly graded, clean crushed stone with 40%
voids serving as a structural layer and temporarily storing water as it infiltrates into the soil
below. To stabilize the surface for paving, a thin (about 1 inch thick) layer of clean, smaller,
single-size crushed stones is often placed on top; this is called the stabilizing course or
choker course. The last layer consists of one or more layers of porous asphalt mixes with
interconnected voids that allow water to flow through the pavement into the stone reservoir.
These porous asphalt layers consist of asphalt binder, aggregates, sands, and recycled
materials and are much like a densegraded hot mix asphalt mixture. By limiting the amount
of fines, the porous mixture allows for more air voids. (Typically between 16% and 22% is
recommended.) It should also be noted that in Figure 1, an optional stone edge is shown
resting on the stone reservoir. This would allow rain to infiltrate into the stone reservoir if
the porous asphalt surface becomes ineffective due to improper drainage (which could be
caused by plugged air voids, for example).
USES FOR POROUS ASPHALT

This material has many uses, including parking lots, driveways, sidewalks, bike paths, and
recreational areas like playgrounds, basketball courts, and tennis courts.

URBAN AND RESIDENTIAL SETTINGS

Porous asphalt serves multiple purposes in both urban and residential areas. It’s widely used
for constructing parking lots, driveways, and walkways. In urban settings, its application
extends to bike paths and recreational areas, including playgrounds, basketball, and tennis
courts. This versatility showcases its adaptability to various environmental and functional
requirements.

ROADWAYS AND STREETS

This type of asphalt isn’t limited to small-scale applications; it has also successfully
implemented in residential and urban street constructions. Its ability to manage water runoff
effectively makes it a preferred choice for such environments, where traditional pavement
might lead to water accumulation and related issues.

HIGHWAY APPLICATIONS

In highway construction, engineers use porous asphalt innovatively. Instead of applying it

as a thin surface layer over conventional highway pavement, they typically use the typical
layered approach with a stone bed. This design allows rainwater to seep through the porous
layer and settle on an impermeable layer beneath, effectively managing water runoff and
reducing the risk of water pooling on the highway surface.

ENHANCED SAFETY DURING RAINSTORMS

One of the standout advantages of this type of asphalt in highway use is its ability to absorb
water from heavy rains. This reduces splash and spray from vehicles, notably trucks,
enhancing visibility for drivers during rainstorms. This feature can significantly reduce the
incidence of crashes and fatalities, making porous asphalt a crucial element in road safety
during adverse weather conditions.

APPLICATIONS

Porous asphalt pavements are typically recommended for parking areas and low-volume
roadways (Roseen, Ballestero, Houle, Briggs, & Houle, 2012). Additional applications of
porous asphalt are for pedestrian walkways, pathways, sports complex applications,
sidewalks, driveways, bike lanes, and shoulders (Hein, Strecker, Poresky, Roseen, &
Venner, 2013). Porous asphalt pavements have also been used successfully for residential
and urban streets as well as highways. Porous asphalt pavements can be installed as whole
or in part with traditional impervious asphalt pavements. When installed in combination
with impervious pavements or adjacent to building roofs, porous asphalt can sufficiently
contain and treat the additional runoff generated.

Design of Porous Asphalt Pavements

There are three considerations required when determining the thickness of the layers of
porous pavements: ● Site considerations to ensure that the site is acceptable. ● Hydrological
design to ensure the porous pavement meets the potential stormwater runoff demands. ●
Structural design to ensure that the porous pavement withstands the anticipated traffic
loading. Most often, the thickness of the stone recharge bed will be controlled by soil
infiltration rates (site considerations) and water quantity (hydrological design) rather than
structural requirements, while the porous asphalt surface layer will be determined by the
traffic loads (structural design)Design of Porous Asphalt Pavements There are three
considerations required when determining the thickness of the layers of porous pavements:
● Site considerations to ensure that the site is acceptable. ● Hydrological design to ensure
the porous pavement meets the potential stormwater runoff demands. ● Structural design to
ensure that the porous pavement withstands the anticipated traffic loading. Most often, the
thickness of the stone recharge bed will be controlled by soil infiltration rates (site
considerations) and water quantity (hydrological design) rather than structural requirements,
while the porous asphalt surface layer will be determined by the traffic loads (structural
design)● Minimum depth to bedrock or seasonal high groundwater should be greater than 2
feet, and frost depth should be taken into consideration. ● Conduct a site evaluation of
sufficient detail to establish site-specific conditions, including soil type. ● The bottom of
the infiltration bed should be flat. For roadways it may be necessary to construct berms
under the pavement surface to retain water on slopes and install drains/overflows at low
points (Roseen, Janeski, & Gunderson, 2011). ● For parking areas, the slope of the porous
pavement surface should be less than 5%. For slopes greater than 5%, the parking areas
should be terraced with berms in between. ● Seek opportunities to route runoff from nearby
impervious areas to infiltration bed. ● Impervious to pervious areas should be less than a
5:1 ratio for most conditions or 3:1 for sinkholesusceptible areas (karst formations). For
systems that will infiltrate water into the soil subgrade, evaluate the site in accordance with
Wisconsin Department of Natural Resources (WDNR) Conservation Practice Standards
1002, “Site Evaluation for Stormwater Infiltration,” and 1008, “Permeable Pavement”
(WDNR, 2004; WDNR, 2014).Hydrological Design Hydrological design determines what
layer thicknesses are required to sufficiently infiltrate, store, and release the expected inflow
of water, which includes both rainfall and excess stormwater runoff from any adjacent
impervious surfaces. This requires information regarding the layer thicknesses and subgrade
permeability along with precipitation intensity levels. The hydrologic design of porous
pavements should be performed by a licensed engineer. The two most common methods for
modeling stormwater runoff are the U.S. Department of Agriculture’s Natural Resources
Conservation Service (formerly Soil Conservation Service) Curve Number method and the
Rational method. The Rational method is not recommended for evaluation of porous
pavement systems. Specific details on hydrological design are beyond the scope of this
report. If a hydraulic connection is possible, porous asphalt pavement systems shall be
located per the requirements of WDNR Conservation Practice Standards 1002, “Site
Evaluation for Stormwater Infiltration,” and 1008, “Permeable Pavement” (WDNR, 2004;
WDNR, 2014)
 .

Figure 2

Porous pavements are often not designed to store and infiltrate the maximum precipitation
at the site. Therefore overflow should be included in the design to prevent stored
stormwater from reaching the surface layers. This will typically involve perforated pipes in
the stone reservoir that are connected to the discharge pipe, as shown in Figure 2. It is also
recommended that an alternative path for stormwater to enter the stone reservoir be
provided in case the surface should become plugged. Figure 2 shows examples of designs
using a stone edge or drop inlet to manage overflows.

Structural Design While limited structural information is available, some porous pavements
have lasted for more than 20 years. For porous pavements carrying light automobile traffic
only, the structural requirements are not significant, and the material thicknesses are
determined by the hydrological design and minimum thicknesses required for porous
asphalts. For porous asphalt pavements expected to carry truck loads, structural design
should follow standard design procedures. Recommended layer coefficients for porous
asphalt pavements are shown in Table 1 (Hansen, 2008). Recommended
minimum thicknesses of the compacted porous asphalt layer for different truck loadings are
shown in Figure 3. WDNR states that a pavement surface infiltration design analysis shall
be conducted using an accepted continuous simulation model (e.g., WinSLAMM) per the
requirements of WDNR Conservation Practice Standards 1002, “Site Evaluation for
Stormwater Infiltration,” and 1008, “Permeable Pavement” (WDNR, 2004; WDNR, 2014).
Those documents also provide prohibited source areas, impervious/ pervious source areas
with equations, and clogging potential ratios.

AGGREGATE STORAGE RESERVOIR

Aggregate storage reservoirs shall be designed to achieve site-specific pavement structural
requirements and stormwater management goals. The aggregate specifications are as
follows per WDNR Conservation Practice Standards 1002, “Site Evaluation for Stormwater
Infiltration,” and 1008, “Permeable Pavement” (WDNR, 2004; WDNR, 2014): ● Use open-
graded base consisting of crushed stone or crushed gravel with no greater than 5% passing
the No. 200 sieve. ● Provide a minimum porosity of 30% per ASTM C29, “Standard Test
Method for Bulk Density (Unit Weight) and Voids in Aggregate.” ● Comply with
soundness, wear, and fracture requirements listed in Wisconsin Department of
Transportation (WisDOT) Standard Specifications Section 301.2.4.5, “Aggregate Base
Physical Properties.” ● Comply with construction requirement in WisDOT Standard
Specifications Section 301.3, “Construction,” or administering authority. Selection of
smaller-size aggregate (e.g., ¾-inch No. 57 stone rather than 3-inch No. 2 stone) will reduce
the rate of discharge along the subgrade slope and the rate of accumulation at the
downgradient end of the system.

Porous Asphalt Mixtures

Porous asphalt mixtures are designed using the Superpave method (50 gyrations) with
requirements for higher air voids and low draindown to assure permeability and
performance. To reduce draindown and provide resistance to scuffing, mixes are typically
designed with polymer-modified binders. Fibers are often added to the mix to reduce
draindown. Mix design recommended specifications are presented in Table 2 (Hansen,
2008).
 PERFORMANCE TESTING

1. Aggregate Tests

Quantitative evaluation of the existence of stone-on-stone contact in the coarse

aggregate fraction of the compacted PA is needed to ensure the design of a mixture with
adequate resistance to both permanent deformation and disintegration . Other aggregate
testing for PA mix is the same with the other asphalt mix which are speciic gravity test,
water absorption test, soundness test, aggregate impact value, aggregate crushing value,
Los Angeles abrasion value and sieve analysis.

2. Binder Tests

Penetration Test

The result of penetration test will indicate the capability of binder in resisting the
permanent deformation due to temperature changes. This test is an empirical test
methods that is used to describe the viscosity characteristics of binder. The
penetration results are expressed as the distance in tenths of a millimeter (10 mm) that
a standard needle of 100 g penetrates vertically into a sample of the material (binder)
at a temperature of 25 。C for loading duration of 5 s.

Softening Point Test

The result of softening point test will indicate the temperature susceptibility the
binde. The softening point is the mean of the temperatures at which the two discuss
often enough to allow each ball, enveloped in bituminous binder, to fall a distance of
25 mm.
Apart from the traditional penetration test and the softening point test, there are other
tests that have been used to test the binder performance for PA. This include DSR,
short term aging, long term aging, FT IR, DTT and WPT. These tests are discussed in
the following sections.

Dynamic Shear Rheometer (DSR) Test

The DSR test is one of the fatigue test for binder. During this test, the value of
torque is measured as well as the phase angle. The critical high temperature of the
binder is deined as the temperature, at which the stiffness value, G*/sin I, of the binder
just exceeds 1.0 and 2.2 kPa on the original condition and RTFO condition,
respectively. The stiffness value of binder will indicate the resistance behavior of
binder towards permanent deformation under the condition of high pavement
temperature. Usually, actual pavement condition will gives much higher stiffness
compare to the virgin and laboratory aged specimens.
The DSR test is conducted to determine the viscoelastic properties of binder such
as the response or dependence of the materials on temperature and loading time. This
test is carried out in a temperature controlled chamber where the tem- perature is
controlled with air or nitrogen gas. The liquid nitrogen usage is kept to a minimum by
switching from gas to liquid nitrogen only when cooling is required. The controlling
mechanism and data analysis is performed by a computer connected to the DSR
equipment.

Short and Long Term Aging Tests

The laboratory aging is carried out on the binder by using rolling thin ilm oven test
(RTFOT) to simulate short term aging and using pressure aging vessel (PAV) aging test
to simulate the long term aging of binder. For RTFOT, each sample is consisting of
35 g of binder. The duration of the test is 75 min.

Fourier Transform Infrared Spectroscopy (FTIR) Test

The FTIR test is carried out to indicate the chemical composition of binder. This testis
important as chemical composition could contribute a major influence on the
rheological, mechanical and adhesion characteristics of the binder. Infrared
spectroscopy is a commonly used technique to identify the functional groups in
organic compounds. This equipment is an effective method to investigate the
chemical composition of the materials. FTIR is a valuable tool to identify the
chemical composition of materials at molecular level. FTIR spectroscopy is using the
infrared part of the electromagnetic spectrum. The absorption of this lower energy
radiation causes vibrational and rotational excitation of groups of atoms within the
molecule.

Direct Tensile Test (DTT)

DTT on binder is performed at constant elongation rates. This test observes the
fracture structure of the specimen. The stress and strain in the bituminous specimen is
also calculated. The maximum stress is considered as the failure stress and the
corresponding strain is the failure strain of the binder. PA mixtures are tested to ensure
their performances. Among the tests are discussed in the following section.

3. Mixture Tests

Cantabro Test
The durability assessment of PA mixtures has been primarily based on phenome-
nological approaches. One of the approach is the cantabro los s test or known as
cantabro test. This test was developed in the 1990s in Spain for assessing PA mixtures.
This testis develop to evaluate and control the raveling los s of PA under dry condition
and soaked condition. The cantabro test is the laboratory test
most commonly used to evaluate durability for mix design and evaluation and to
conduct research on PA mixtures. The design procedures of PA in many countries
overlook the influence of aging and temperature on the raveling. Therefore, it is
necessary to investigate the raveling characteristic of PA in order to ensure the
durability of PA. The cantabro testis viewed as the best test method for investigating the
raveling behavior of PA. The test conditions consisted of standard condition, soaked
condition, low temperature condition and freeze-thaw condition.
In the cantabro test, a compacted marshall specimen is placed in the Los Angeles
abrasion machine (without steel ball) and subjected to 300 revolutions. The cant- abro
loss, expressed in percentage, corresponds to the ratio of lost weight to initial weight of
the compacted specimen. This test is also important to investigate the particle loss of
PA mixture. In addition, cantabro test can be used to evaluate the performance of PA.
Lastly, this test will indicate the lower limit of binder content for optimum binder
content (OBC) determination for PA.

Binder Draindown Test

Binder draindown test is performed to measure the binder lost from the loose mix
placed in a drain down basket (No. 4 mesh size) and conditioned at the mixing
temperature for 3 h with the draindown being measured every hour. This test shows the
amount of binder draindown relative to the total weight of the mix. A maximum
draindown of 0.3 % by weight of total mix is typically the maximum value for
draindown of PA mix. The drained binder will drop onto the tray below the basket.
The mass of retained of binder is calculated by the value of initial mass minus the
mass of drained binder. This test will indicate the upper limit of binder content for
optimum binder content (OBC) determination of PA.
The irregular distribution of binder generated by its draindown can lead to
raveling of zones with low binder content and reduce the permeability in the zones with
accumulated binder. The occurrence of binder draindown through the specimen will
reduce the permeability of mix.
 Indirect Tensile Strength Test (ITS)

The indirect tensile strength test (ITS) is carried out to provide an indication of the
mechanical performance of asphalt mixtures. The ITS testis the test to evaluate the
moisture susceptibility for asphalt mixture. Due to porous nature of PA spec- imens, it
is impossible to archived the level of saturation required by typical test procedures
similar to AASHTO T283 standards. Therefore, the saturation step is omitted when
testing the PA mix due to the PA specimen becoming easily saturated just by soaking in
the water bath. This testis essential to indicate how well the
binder can bond with aggregate and evaluate the adhesion between those materials
. Figure 3 illustrates the ITS machine.

In addition to assessing the strength of the mixtures, the potential for moisture
induced damage is also determined based on the tensile strength ratio (TSR). The TSR
is calculated as the ratio of the wet ITS to the dry ITS (ITSwet/ITSdry × 100 %). The
minimum value for the T SR of PA mixtures differs according to the require- ments of
road authorities, but typically the required TSR value is to be greater than or equal to 80
%. Besides that, the stiffness characteristics of indirect tensile stiffness modulus (ITSM) is
also can be determine to evaluate the load spread ing ability of mixtures in pavement.
After compaction and cooling, the specimens will be tested at 30 °C with Nottingham
asphalt tester (NU-10). The test results will established the value of ITSM. The
evaluation of moisture susceptibility based on the retained tensile strength ratio (TSR) is
determined using the modiied Lottman method was recommended in 2002 for PA mix
design.

Fig. 3 ITS machne

 Permeability Test

Drainability is one of the most important characteristics of PA, since it is closely

related to several of the advantages exhibited by PA especially under wet weather.
However, most agencies do not specify the direct or actual measurement of the
coeficient of permeability or permeability value. Thus, most common approaches in
determining the permeability are targeting a minimum total air void (AV) content value
as an indirect index of adequate permeability and the optional measurement of
permeability on laboratory compacted specimens. For these optional mea- surements, a
minimum permeability value of 100 m/day was suggested by NCAT and ASTM
international (D 7064-04). However, the s election of minimum values of permeability
should be conducted based on the actual rainfall events expected at the project location
or country due to different countries are having different rainfall period and intensity for
different countries .
The permeability of PA is measured using the falling—head procedure. The irst step
is to prepare a specimen where the specimen is wrap in plastic around the s ides to force
the water to exit through the bottom of the specimen instead of the perimeter of
the specimen. After the specimen is secured in the standpipe, the specimen is
initially saturated with water by illing the outlet pipe. The standpipe is then illed with
water. The effective porosity is used due to the fact that only the accessible voids will
contribute to the permeability of the specimens.

Repeated Load Indirect Tensile Test (RLITT)

Repeated load indirect tensile test (RLITT) is performed to determine the resilient
modulus of the asphalt specimens. This test is conducted at low s tress levels not
exceeding 10 % of the failure stress to ensure linear response of the materials . The
RLITT is performed using universal testing machine (UTM). This equipment has a
temperature controlled chamber for maintaining constant temperature during the test.
During testing, the loading are applied along the vertical diameter o f the specimen and
the resulting deformations along the horizontal diameters are mea- sured]. Figure 4
shows the UTM machine.
Fig. 5 APA machine

associated with permanent deformation of PA. Figure 5 illustrates the APA machine.
Besides APA test, the Hamburg wheel tracking test is used for determining the rut
resistance of PA. Due to the open-graded proportion of the PA mix, rutting potentials
related to scattering and instability will be the major problem. In this test, the specimens
are separated into two groups, respectively in a 60 。C air bath and a 40 。C water bath.
The pre-heat time is 4 h for the 60 。C air bath and 2 h for the 40 。C water bath]
The rut resistance of PA mix can also be carried out for the specimens that have been
immersed in the water for a long period. This is called the immersion rutting test. For
this test, the specimens are put into a water bath of 60 。C for 48 h. The result from
this study will indicate the stripping rate of the PA mix.
Fig. 6 Scanned and cleaned image of PA

Compression Test
The triaxial compression testis the test that can reflect the actual road conditions of the
asphalt mixture. The unconined uniaxial tests may underestimate the strength of PA.
The shear strength indexes can be obtained from this test and used for road design
based on a shear strength criterion. The specimen is made by either a gyratory
machine or marshall compactor process.

Aging Effects
The aging test for short term oven aging and long term oven aging are implemented
using marshall compacted specimens. The comparison of PA mixture properties
subjected to these two aging tests proved inconclusive. Additional work on PA mixtures
should be conducted in order to obtain more conclusive results.
Image Analysis
To quantify the vertical pore distribution of PA, the areal porosity where the ratio of the
area of the pores to the total area of the sample is used. However, the larger an area
used, the less resolution of the porosity distribution. The smallest area that yields a
representative porosity value for that location in the PA sample is called the
representative elemental area (REA). Figure 6 shows scanned and cleaned image of PA
sample where pores are shown as black in the image. One of the equipment that is
capable in capturing this image is COSMOS image analysis software
3. Field test
The first type of test for testing PA at ield is the grain size analysis. Usually, sieve and
hydrometer analyses in accordance to ASTM D422-63 are performed to obtain the grain
size distribution of the vacuumed sediments. These sediments are then classiied
according to the uniied soil classiication system. Then, the percentage of organics is
determined by loss of ignition testing in accordance to ASTM D7348-08. The third testis
the compaction parameter. The estimation ofield compaction of PA pavement is
crucial in order to ensure the PA is achieving the targeted density, at the same time
to predict the construction costs. This testis also important for the design optimization of
PA pavements. Next testis skid resistance test. This test is important to indicate the
drainability performance of PA can reduce the road surface water, which means that
aquaplaning at high speed is not likely to occur. In addition, air voids can permit the
surface water to drain quickly out the road surface, thus reducing spray and enhance
the drivers ’ visibility. Sound absorption coeficient value from sound adsorption test
can characterize the sound absorption properties of PA. The flow characterization
test, water quality measurement, sediment analysis and rainfall characterization are also
can be done in order to determine flow characteristics of PA at certain area like parking
lot.
 CONSTRUCTION
One of the most important concerns during the construction of porous asphalt pavements is
the clogging of the surface or filling of the voids in the stone reservoir. As a result,
protecting the pavement during construction from uncontrolled runoff in adjacent areas and
the surrounding soil from compaction is critical. This includes having temporary stormwater
controls in place until the site is stabilized and clear, specific guidance for construction
procedures. Typical guidelines for construction procedures for porous pavement include the
following: ● Plan to construct the porous pavement as late as possible in the construction
schedule. ● Protect site area from excessive heavy equipment running on the subgrade,
compacting soil, and reducing permeability. If the subgrade soil is overcompacted during
construction, consider refracturing or ripping the soil subgrade to a depth of 12 to 20 inches.
Additional base/subbase aggregate may be needed, as well as additional compaction of
these materials, to reduce the risk of surface settlement and to render a stable structure for
supporting vehicular traffic. ● Excavate the subgrade soil using equipment with oversize
tires or tracks to minimize compaction to soil. ● As soon as the bed has been excavated to
the final grade, the fabric filter should be placed with an overlap of a minimum of 16
inches. Use the excess fabric (at least 4 feet) to fold over the stone bed to temporarily
protect it from sediment. ● Install drainage pipes, if required per WDNR Conservation
Practice Standards 1002, “Site Evaluation for Stormwater Infiltration,” and 1008,
“Permeable Pavement” (WDNR, 2004; WDNR, 2014). ● Place the aggregate stone
recharge bed carefully to avoid damaging the fabric. The aggregate should be dumped at the
edge of the bed and placed in layers of 8 to 12 inches using tracked equipment and
compacted with a single pass of a light roller or vibratory plate compactor. ● When using a
stabilizer course, it is important that the aggregate be sized properly to interlock with the
aggregate in the recharge bed. The stabilizer course should be placed at a thickness of about
1 inch. Some larger stones from the stone reservoir should be visible at the surface.● The
porous asphalt should be placed in 1- to 4-inchthick lifts, and tracked pavers are
recommended. ● The porous asphalt should be compacted with two to four passes of a 10-
ton roller. ● Restrict traffic for at least 24 hours after final rolling.
 MAINTENANCE
In order to maintain long-term performance of porous asphalt pavements’ stormwater
management capabilities, it is recommended that the surface infiltration rates be inspected
annually during rain events to observe any changes in effectiveness of infiltrating
stormwater. To remove any solids and debris that could lead to more permanent clogging of
the pavement, it is recommended that porous asphalt pavements be vacuumed two to four
times a year or power-washed (UNHSC, 2012; Palmer, 2012). Best practice is to
recommend conducting surface cleaning operations during spring and fall. During winter
months, there are no special requirements for plowing. Deicing chemicals may be used to
melt ice and snow from the surface, but the amount of deicing chemicals will be
significantly less than for impervious pavements. Do not use sand or cinders as they will
clog up the air void spaces within the pavement structure. The appendices to this
publication include more detailed inspection and maintenance guidance for porous
pavements. These appendices were adapted from materials published by UNHSC (UNHSC,
2011; UNHSC, n.d.; Hall, n.d.).
NB. Porous asphalt pavements should never be seal coated or crack sealed. If patching is
necessary, conventional mixes may be used if less than 15% of the pavement area is
affected. Porous asphalt may not be used in industrial storage and loading areas or vehicle
fueling and maintenance areas. See WDNR Conservation Practice Standards 1002, “Site
Evaluation for Stormwater Infiltration,” and 1008, “Permeable Pavement” (WDNR, 2004;
WDNR, 2014).d
 CONCLUSTION
In conclusion, this case study demonstrated the feasibility and benefits of using porous
asphalt pavement for stormwater management and road safety. The performance of the
porous asphalt pavement was evaluated based on its infiltration capacity, structural
integrity, and surface friction. The results showed that the porous asphalt pavement
maintained a high infiltration rate throughout the study period, even under heavy rainfall
events. The structural performance of the pavement was also satisfactory, as no significant
cracking, rutting, or raveling was observed. The surface friction of the pavement was higher
than that of conventional asphalt pavement, indicating a better skid resistance and reduced
splash and spray. Therefore, porous asphalt pavement can be considered as a viable and
sustainable option for urban areas with high traffic and rainfall intensity.