Lighting Design Values

Recommended values for illuminance, luminance, and small-target visibility are pub­lished as Tables 2, 3, and 4 in ANSI/IESNA RP-8-00, American National Standard Practice for Roadway Lighting, www. iesna. org. These lighting criteria for the three recognized calculation methods are typically adopted by AASHTO and published as a part of the AASHTO Guideline for Roadway Lighting. The Federal Highway Administration, in turn, historically has accepted the RP-8 criteria as adopted by AASHTO for lighting projects partially funded with federal funds. Refer to the latest edition of the AASHTO Roadway Lighting Design Guide for current recommended criteria. Each lighting designer should have access to the latest versions of these docu­ments, which sometimes contain substantial modifications.

7.17.2 Other Considerations

In using the AASHTO tables, there may be conditions for which different luminance and illuminance levels are desirable or necessary. The lighting designer should use all available pertinent information in reaching a decision regarding the level to be used for any specific street or highway.

There are many locations where very high levels of luminance or illuminance are provided for streets in the central city business district. This is usually a commercial consideration directed toward making the downtown business area more appealing to shoppers. Levels considerably higher than the levels in the table must be justified on some basis other than solely for the safe and efficient flow of traffic. If higher than recommended levels are desired, the lighting designer should consider using a white light source, such as metal halide, rather than a monochromatic source, such as high- pressure sodium (HPS). Visibility tests have shown there is a lack of contrast with high levels of HPS. The lack of contrast reduces the ability to distinguish an object from its background, the details of an object, or the color of the object.

Freezing Induced Water Flow

The significance of the coupling between heat and water transport will be illustrated using a freezing experiment performed by Mizoguchi (1990). He packed four iden­tical cylinders with Kanagawa sandy loam. Each cylinder was 20 cm long and had an internal diameter of 8 cm. The samples were prepared for the freezing test by bringing them to the same initial state involving a uniform temperature of 6.7 °C and a close to uniform volumetric water content of 0.33 throughout the cylinders. Water and soil in each cylinder was subjected to freezing from the top down, since their top covers were exposed to a circulating fluid with a temperature of -6 °C. One cylinder was used to obtain initial values, and the other three were removed from freezing after 12, 24 and 50 hours respectively. The cylinders were then cut into 1 cm thick slices for which the total water content (ice + liquid water) was

04*

d

0 0*

Fig. 11.6 The simulated volumetric water content, 9, in a model road (a) after a light rainfall event (top), (b) after a heavy rainfall event (middle), (c) after a moderate rainfall event using small fracture-zone permeability (bottom) The particles illustrate the flow paths of the infiltrated rainwater. The vertical scale is exaggerated for clarity

determined. The experimental procedure thus described was then reproduced in a computer model in order to test the model.

As described in Chapter 4, Section 4.6, water flows towards freezing fronts where it changes phase from liquid to solid. This process is clearly evident in Fig. 11.7 where the total water content in the upper half of the cylinder increases as the col­umn freezes (Hansson et al., 2004). Since freezing is a relatively quick process, extremely high hydraulic gradients emerge and can lead to sometimes very rapid upward flow of water. The freezing front is clearly visible in Fig. 11.7 as the depth interval where the total water content decreases rapidly. The calculated results are in fair agreement with the measured values. Specifically, the rapid decrease in the total water content at, or immediately below, the freezing front and the gradual recovery deeper in the columns is well predicted.

It is the dramatic redistribution of water caused by the freezing that causes frost heaving, which may damage roads even though the largest problems occur in con­nection with thaw weakening. It should, however, be pointed out that the computer

Fig. 11.7 Simulated (symbols) and measured values (horizontal bars) of the total volumetric water content 0, 12, 24 and 50 h after freezing started. A variable convective heat transfer coefficient, hc, was used for the first simulation (solid circles) and a heat leakage bottom boundary for the second (open circles). Simulated values were averaged over 1-cm intervals

model used here neglects effects of frost heave. If the conditions for frost heave had been met during the simulation, the result had been different since the liquid pressure head would have changed as an effect of a relative ice pressure not equal to zero.

Simulating the Infiltration and Percolation in a Road After Rainfall

Hansson et al. (2005) made an attempt to illustrate the effect of a rain shower and fracture zone permeability on the subsurface flow pattern using a two-dimensional computer model; thus making the simulation domain more like reality (Fig. 11.6). The properties of the materials used in the various layers of the model road fulfil the requirements of the Swedish road design guide. In addition, it was assumed that the asphalt layer of the road had plenty of fractures over a relatively short distance, “a fracture zone”, which thus enabled the use of an equivalent homogeneous porous media model. More details about material properties, driving data etc. can be found in Hansson (2005).

Notice (Fig. 11.6) that the fracture zone captures most, if not all, of the upstream surface runoff for the light rainfall event. The heavier rainfall causes a significantly larger infiltration in the road shoulder since the infiltration capacity of the fracture zone, or the granular base layer beneath it, was exceeded. As a consequence, a larger fraction of the total surface runoff reached the road shoulder, and the region of the roadside where both rainfall and surface runoff infiltrated was considerably ex­panded laterally. This result is qualitatively supported by the findings of Flyhammar and Bendz (2003) who measured concentrations of various solutes in the shoulder and beneath the asphalt cover in a Swedish road partly built with alternative materi­als, generated from waste and residuals. These materials contained plenty of solutes, and the leaching pattern is similar to the simulated water flow pattern, although the leaching patterns exhibited a large variability between solutes.

Examples

11.4.1 Modelling of Moisture Movements

Alonso (1998) presents, on the basis of in-situ measurements, relevant aspects of the water content development of pavement layers and its effect on the mechanical characteristics of granular bases and subgrades. A general model for the coupled analysis of transfer processes (water, heat) and stress-strain behaviour of unsatu­rated compacted soils is then presented. A review of some representative properties of compacted soils has been carried out from the perspective of modern concepts of unsaturated soil mechanics. As an application of the methods described a full simulation of a modern pavement structure under the effects of a Mediterranean cli­mate has been developed. The last section of Alonso’s paper is devoted to collapse and swelling phenomena of subgrades. Collapse is found in some natural lightly cemented soils but it is more common in embankments compacted on the dry side of the optimum water content. A real case involving severe collapse deformations and the role of described models to analyse the problem is presented. Finally, the available techniques to design and analyse the behaviour of highways on expansive soils are presented.

1

0.9

0.8

0.7 ro

0.6 IS

0.5 о

0.4

0.2 0.1 0

Alonso et al. (2002) also presented an analysis of the optimum position and depth of longitudinal drains in pavements. An analysis of different climates on the over­all pavement behaviour is then given. Three climates have been defined: Tropical, Mediterranean and Sub-alpine (see Chapter 1, Section 1.11), which were defined on the basis of actual data involving rainfall, temperature and relative humidity records. Five years of climate were simulated and the reaction of the selected pavement struc­ture and drainage position were computed and discussed. Figure 11.4 shows some of the computed results. It can be seen that the addition of longitudinal drains has a profound effect on the granular base and sub-base saturation over time, whereas their effect on the subgrade, Fig. 11.5, was found to be more limited. Longitudinal

b)

0 2 4 6 8 10 12 14

m

Fig. 11.5 Distribution of degree of saturation for a pavement in a Mediterranean climate. Evapora­tion through pavement allowed. (a) 1st July, (b) 1st December, adapted from Alonso et al. (2002)
drains are capable of maintaining a fairly well drained subgrade platform under a Mediterranean climate (as illustrated) whereas their effect was found to be more limited under sub-alpine or tropical climates.

STREETS AND HIGHWAYS OTHER THAN FREEWAYS

Fixed roadway lighting systems increase night visibility, as well as improve safety, traffic movement, and general roadway use. Traffic volume, numbers of pedestrians, at-grade intersections, turning movements, signalization, and unusual geometrics are some elements that make lighting of streets and highways desirable. Lighting, in addi­tion to its safety benefits, is a crime deterrent and a valuable aid to law enforcement agencies and often contributes to the pride of a community.

7.17.1 Warranting Conditions for Roadways Other Than Freeways [3]

It is not practical to establish specific warrants for the installation of roadway lighting to satisfy all prevailing or anticipated conditions. In general, lighting may be consid­ered for those locations where the respective governmental agencies concur that light­ing contributes substantially to the efficiency, safety, and comfort of vehicular or pedestrian traffic. Lighting may be provided for all major arterials in urbanized areas. It may also be provided for locations or sections of streets and highways where the ratio of night accidents to day accidents is higher than the statewide average for similar locations and a study indicates that lighting may be expected to significantly reduce the night accident rate. Determinations to install lighting that have been made on the basis of accident experience at a particular site can be applied to other similar highway locations. The latter should include similar geometric layouts on which experience or accident data are not available and also on highway sections where anticipated increase in vehicular and pedestrian traffic will present problems within a few years. Lighting may be considered at locations where severe or unusual weather or atmospheric conditions exist. In other situations, lighting may be considered where the local govern­mental agency finds sufficient benefit in the form of convenience, safety, policing, community promotion, or public relations to pay an appreciable percentage of the cost of, or wholly finance, the installation, maintenance, and operation of the lighting facilities [3].

Lighting has been successfully used on rural conventional highways at hazardous locations to reduce the number of accidents. Lighting of spot locations in rural areas

should be considered whenever the driver is required to pass through a section of road with complex geometry and/or raised channelization as well as at intersections with higher than normal accident rates [3]. Isolated lighting of railroad grade crossings has been used to help the driver identify when a train is present in the crossing.

As with any roadway or intersection, warranting conditions should also be applied at a roundabout to determine the need for lighting. If lighting is warranted, the round­about should be lit to a level that is 1.3 to 2 times the values used on the best lit approach and the uniformity should be 3:1 or better. The lighting should be extended a minimum of 400 ft (122 m) along each road connecting to the roundabout. Providing lighting that will provide good pedestrian recognition is an important issue. Placement of light poles 10 to 30 ft (3 to 9 m) before the crosswalk is recommended as a means of accomplishing this task [7].

HARBINGER

The Harbinger is the Dutch hip version of the Bodega described on page 168. In this case, a bump – out provides enough space for an additional bedroom or sitting room downstairs. If one were to count the loft, this house would actually measure almost 600 square feet, or 700, with the add-on.

Square feet: 278

With add-on: 372 House width: 20’

House length: 20’

Porch: 6’ x 13У2

Great Room: 9’x13’ Kitchen: ІУ2 x ІУ2

Bathroom: 51/2’ x 51/2’

Addition: 93/V x 7’

Ceiling height: 7’ 6”

Loft height: 7’

-sizes are approximate

Historical and cultural landmarks

The Bronze Age begins with the Shang Dynasty, succeeding the Xia Dynasty about 1600 BC. This aristocratic and cruel regime is well known in archaeology; the first texts scratched in bone come from it. The influence of this dynasty is limited to the valley of the Yellow river to Shandong. Then about 1100 BC the Zhou, coming from the valley of the Wei (a tributary of the Yellow River in Shaanxi) supplant the Shangs. Under their more humane domination the Chinese civilization reaches not only further to the north, but also and especially toward the south as far as the Yangtze valley. The Zhou estab­lish their capital near Luoyang where the river flows out onto the plain. But the Zhou regime does not have a structure that is capable of coping with the growth of their domain. Several centuries after their advent, provincial powers begin to rival the influ­ence of the central power. This marks the onset of the feudal period, beginning with what is called the Spring and Autumn period (771 – 480 BC) and the Warring States peri­od (480 – 221 BC), a rather evocative name indeed.

The major currents of Chinese thought developed during this troubled period.[374] [375] Kong Fuzi, or Confucius lived from 551 to 479 BC and founded a social philosophy that seeks to establish justice and equity in the framework of traditional structures and cus­toms. Confucianism preaches peace, order, and return to the path of the “wise kings of Antiquity”, motivated by the desire to bring well being to the people. Later this becomes the official doctrine of the empire’s administrators, mandarins recruited competitively based on their literary knowledge. The principle disciple of Confucius, Meng Ke, or Mencius, was born in 374 BC and becomes counselor to the princes of the kingdoms of Liang and Qi. He brings the humanist aspects of Confucianism to the forefront: tradi­tions and customs are made for men, and not vice-versa. Opposing this trend of thought, Taoism appears at an indeterminate date during this same period. One of its best-known founders is Laozi (Lao-Tse), who lived in the 4th century BC. Rarely has a philosophy been so caricatured. Nonetheless, it contains the real premises of scientific thought. As a naturalist philosophy, based on observation of natural things, Taoism has as its ideal the search for causes, but without any aspiration to discover at all costs a unique model that might explain everything. Taoist thought, based in observation and experimenta­tion, is more descriptive than explanatory:

“All phenomena have their causes. In the ignorance of these causes, it can happen that one is correct (in regard to the facts), but it is as if one knows nothing, and in the end remains per­plexed. [….] The fact that water exists in the mountains and heads toward the sea does not arise from some antipathy for the mountains, nor from a love for the sea, it is simply due to the effect of altitude such as it is.”11

So, whereas Confucianism is oriented to action, Taoism is the calm search for an interior pathway. Naturally humble, it nonetheless willingly arrays itself against the powerful.

During the feudal period scholars move from one court to another. The more enlightened of the princes of these kingdoms create academies, the most celebrated being at Linzi, the capital of Qi in Shandong.[376] It is from within this academy that Zou Yan (305 – 240 BC), considered by Joseph Needham[377] to be the founder of Chinese sci­entific thought, formulates the theory of the five elements: water, fire, wood, metal, and earth.

“Of the five elements, the first is called Water, the second Fire, the third Wood, the fourth Metal, and the fifth Earth. Water (is the quality in nature) that moistens and tends to sink; Fire (is the quality in nature) that flames and tends to rise. Wood (is the quality in nature) that per­mits curved surfaces or straight edges. Metal (is the quality in nature) that can follow (the shape of a mold) and can harden. Earth (is the quality in nature) that permits sowing, (growth), and harvest.”[378]

This text shows how the Chinese view is something quite different from the Greek the­ory of four elements, popularized at about the same period by Aristotle.[379] The Chinese theory of five elements is not a model intended to explain nature, but rather a classifica­tion of processes or physical properties (Table 8.1). The theory is essentially descrip­tive, consistent with Taoism. It will be used throughout the evolution of Chinese thought, completing the vision well known in the West of competition between the opposing principles ying and yang.

Table 8.1 Correspondence among the five elements of the Chinese literati and a classification of their physical properties.

Element Physical Property

Water

That which is fluid, can flow, and dissolve

Fire

That which emits heat and can burn

Wood

That which is solid and can be shaped (carved)

Metal

That which is solid and can be melted, and which can take the form of a mold

Earth

That which produces useful plants

The first dynasty of the imperial era, that of the Qin, is followed by the long Han Dynasty. The Romans maintained commercial relations with this dynasty and may have even had diplomatic relations.[380] From 221 BC to 190 AD, China knew four centuries of unity.

The feudal period and this first imperial era experience intense economic and demo­graphic development, both supported by hydraulics as we will see further on. The cen­sus of year 2 already reports more than 57 million inhabitants.[381]

The fall of the Han Empire is first followed by a splitting of China into three king­doms (220 to 310 AD) and then by a period of total anarchy (310 to 589 AD). These long centuries of chaos are often called the “Chinese middle ages”. It is in the 3rd cen­tury that Taoism, a philosophy but also an inspirational movement of secret societies, becomes a religion as well. In the 3rd and 4th centuries, Buddhism is introduced and develops in China.

In 589 AD China is reunified under the Sui and Tang dynasties. After a troubled period from 906 to 960 The Song Dynasty is again established, and under it the natural­ist Chinese movement reaches its greatest development. But starting in 1127 the power of the Songs recedes in South China following a series of invasions. From 1271 the Mongols occupy all of China and call themselves the Yuan Dynasty. The Mongol Empire extends from Persia to the Sea of China, naturally favoring commercial relations between China and the Middle East. In 1368 the Mongols are chased out by the Mings following peasant insurrections caused by famine. The Mings are eventually succeeded by the Manchu Qing Dynasty from 1644.

Naturalist Chinese thought is the inheritor of Taoism and excels in the observation and classification of things. But thanks to Confucianism, oriented toward action and often impelled to relieve manual labor, the Chinese invent many devices that spread toward the West. These include the axial rudder, the wheelbarrow, the magnetic com­pass, gunpowder, and the navigation lock. The Chinese excel in hydraulic technology as we will see further on in this chapter. But ancient Chinese science also uses mathe­matics to describe the laws of nature. The Jesuits, who get established in China during the Qing Dynasty in the 17th century, bring with them the methods of modern science.

We have seen that hydraulics is in the fabric of the founding legend of Chinese civ­ilization. Since the very beginning of Chinese history, hydraulic technologies are employed to make new lands productive through irrigation and drainage of swampy val­leys. Hydraulics is also brought to bear on the development of the infrastructure for waterborne transport. But there is no relief from a recurrent curse that returns regular­ly: floods and the associated changing courses of rivers, killing people and ruining entire regions. The inability to stabilize the large rivers, in particular the Yellow River, is often the cause of popular uprisings that end up bringing down dynasties. We therefore pro­ceed to describe this great river, one of the principle actors on the vast stage of China.

From the beginnings of agriculture to the legendary founder of Chinese civ­ilization

Archaeology teaches us that grain cultivation, namely millet, appears in the middle basin of the Yellow River around 6000 BC.[370] [371] [372] Two cultures develop successively in this region: one is called the Yangshao at the end of the VIth millennium BC, during which small- scale farming develops (pork, poultry); the other is the Longshan, at the end of the IIIrd millennium BC, during which wheat and barley develop in addition to millet, and the first fortified villages appear. As a point of reference, recall that this is also the period of the grand civilization of Harappa on the Indus and its extensions in Bactria. The Chinese regions involved are Shaanxi, Shandong and especially Henan and Shanxi. The foundation of Chinese civilization is rooted in the continuity of this culture, localized in

7 v 8

the region of the confluence of the Luo and the Wei rivers with the Yellow River. The legendary hero is Yu the Great who is said to have tamed the unpredictable course of the Yellow River through the construction of canals and deepening of its bed:

“Before him, the overflow waters flowed wantonly”[373]

It is of course, impossible to know if all the accomplishments attributed to Yu result­ed from his efforts, or indeed from human intervention at all. But, given what we know and taking into account the seriousness of the ancient Chinese sources, there is no rea­son to doubt a priori the existence of the personage himself. He would be at the origin of the Xia Dynasty, whose domain scarcely extended beyond the terraces and valleys that mark the terminus of the middle course of the Yellow River. Taking the suggestions of the ancient Chinese historians to their logical conclusions, one ends up dating the leg­endary reign of Yu the Great to around 2200 or 2000 BC.

Civilization in China apparently begins two millennia after it began in Mesopotamia. On the other hand this Chinese civilization is remarkable for its durability, from its earliest beginnings up until the present day.

From the beginnings of agriculture to the legendary founder of Chinese civ­ilization

Figure 8.1. The eastern portion of China, showing the middle and lower courses of the Yellow River (Huanghe) and the Blue River (Yangtze). On this map, the rivercourses, coastlines, and city and province names are those of today. The Grand Canal is not shown.

Special Conditions That Warrant Lighting [3]

Continuous, complete, or partial interchange lighting is considered to be justified in

the following situations:

• In general, lighting is warranted where the local government agency finds sufficient benefit in the forms of convenience, safety, policing, community promotion, public relations, etc., to pay an appreciable percentage of the cost of the installation, main­tenance, and operation of the lighting system.

• Where there is continuous freeway lighting, there should be complete interchange lighting.

• Where complete interchange lighting is warranted but not initially fully installed, a partial lighting system that exceeds the normal partial installation in number of lighting units is considered to be justified.

• Lighting of crossroad ramp terminals is warranted regardless of volumes where the design requires the use of channelizing or divisional islands, and/or where there is poor sight distance.

7.16.3 Freeway Lighting Design Values [7, 8]

The following should be satisfied for proper design when using the illuminance method:

• Continuous freeway and complete interchange lighting should be designed to provide an average maintained horizontal illuminance in the range of 0.6 to 0.9 fc (6 to 10 lx) on the traveled roadway.

• The ramps should be lighted to the same level as the main roadway.

• The point of least illuminance on the roadway should not be less than 0.2 horizontal fc (2 lx).

• An average to minimum uniformity ratio of 3:1 or 4:1 is reasonable. The more uniform design is preferred.

• The higher levels of illuminance should be at the gores and intersections.

• Situations such as high ambient brightness near the roadway or closed circuit tele­vision surveillance equipment may justify higher levels of illuminance.

The following criteria should be satisfied for proper design when using the luminance

method:

• The average maintained luminance should be in the range of 0.4 to 1.0 cd/m2 (0.12 to 0.29 foot-lambert, or ft-L).

• The ratio of average luminance to minimum luminance should not exceed 3.5 to 1.

• The ratio of maximum luminance to minimum luminance should not exceed 6.0 to 1.

• The ratio of veiling luminance to average luminance should not exceed 0.3 to 1.

7.16.4 Transition Lighting

Rapid changes in lighting levels which occur, especially when leaving a continuously lighted section of roadway, may be compensated for by using transition lighting or adaptation techniques. Lighting levels as recommended above should be reduced to approximately one-half the recommended level for about 15 s to allow the eye to adapt.

7.16.5 Bridges and Overpasses

Lighting on bridges and overpasses should be at the same level as the roadway. It may be desirable to provide lighting on long bridges in urban and suburban areas even though the approaches are not lighted, since lighting enhances both the safety and utility of bridges. Where bridges are provided with sidewalks, lighting is warranted to increase pedestrian safety and security.

Test Results

There are a number of impressive publications in the technical literature that describe the results of testing antinoise properties of various pavements. (Refer to the Bibliography at the end of this book.)

Olszacki (2005) tested the sound-absorbing power of different asphalt surfacing types with diversified void contents. Figure 12.5 shows the relationship between the noise absorption coefficient and sound frequency. It is evident that SMA is character­ized by better properties than mixtures of AC, but not as good as porous asphalt with a much higher content of voids, from 10-22% (v/v).

Other research has also stated that pavement noise increases along with an increase in the maximum particle size of the wearing course mixture. Therefore, when antinoise properties are at issue, mixtures SMA 0/5 and 0/8 instead of 0/11 and 0/16 mm are preferred. Generally, the macrotexture of SMA makes it quieter

image150

Frequency (Hz)

FIGURE 12.5 Impact of asphalt mixture type on noise absorption. (From Olszacki, J., The determination of the water permeability and noise absorption of asphalt concrete used in porous courses [Okreslenie wodoprzepuszczalnosci i dZwiekochlonnosci betonoasfaltow sto – sowanych w nawierzchniach drenujacych], Ph. D. thesis, Kielce University of Technology, Poland, 2005. With permission.)

than AC by about 1-2 dB(A). When coarse SMA 0/16 is used, an increase in the noise level of about 1 dB(A) is reported (Sandberg, 2001). SMA’s distinctive fea­ture—namely, the grit of 2/4 or 2/5 mm aggregates—makes the pavement noisier, which is why gritting with finer aggregate is recommended. After some time, when the grit been removed by traffic, the SMA noise level will naturally reduce. So the conclusion may be drawn that the SMA antinoise properties change over the ser­vice life of the pavement. A site investigation (Schmiedlin and Bischoff, 2002) has proved that a classic SMA pavement is only slightly quieter than classical AC.

Finnish tests of SMA antinoise properties (Valtonen et al., 2002) have pointed out another problem when studded tires are permitted. Testing using the close-prox­imity (CPX) method was conducted at a speed of 50 km/hr. In spite of the SMA 0/5 mm having the best properties just after laydown (in comparison with SMA 0/8, 0/11, and 0/16), a deterioration in properties due to wear caused by studded tires was found after the first winter of operation (only 1 year of service life). Under these circumstances, the SMA mixture’s resistance to wear by studded tires should have been taken into account. The coarsest SMA gradation is more resistant to studded tire wear, in contradiction to its antinoise properties. Consequently, it has been con­cluded that SMA 0/8 and SMA 0/11 might be more appropriate than finer SMA 0/5 (in this research, SMA 0/5 has worn 10 times as much as SMA 0/16). In testing done in the United States, SMA 0/12.5 and SMA 0/9.5 mm were compared using the CPX method (Bennert et al., 2004). The results proved the increase in noise at the contact between tires and pavement along with the increase of SMA maximum aggregate size.

Table 12.2 shows the collective comparison of SMA properties with a reference mixture of AC. The new concept of a silent SMA characterized by better properties than classical SMA is presented in Chapter 13.

Test Results Подпись: Reported Reduction db(A)a Reference + 2.0 to -2.0c BA 0/11 + 5.0 to + 7.0 BA 0/15 + 1.4 to + 1.6 BA 0/16 + 0.2 to + 0.6 0.0 to -2.0** + 0.8 to -0.5 + 1.0 to -3.0**) + 5.3 to + 5.2 Hot Rolled + 3.5 to + 3.2 Asphalt + 2.7

Source: From EAPA, Heavy duty surfaces. The arguments for SMA. European Asphalt Pavements Association (EAPA), 1998, With permission. a Negative values indicate an increase in noise level. b Calculated value.

c When the surface is treated with uncoated chippings smaller than 2 mm.