Research Trends and Results

Progress of Future Road Traffic Noise Abatement
KADOYU Katsunori, HeadYOSHINAGA Hiroshi, Senior researcher (Dr. Engineering)
Road Environment Division, Environment Department（Key words）

Road traffic noise ,loud vehicle, Enlightenment, Eco-driving

1. Actual state of the Road traffic noise
Noise barriers, porous asphalt concrete pavement
and vehicle noise emission limits have improved theachievement status of environmental quality standardof automobile noise (in the area facing the road) toapprox. 92% on 2011 from approx. 77% on 20001).
However, as it is difficult to achieve 100% over a shortperiod only through conventional noise abatement
measures, we need other measures based on a new idea.
Fig. 1 shows the measured value of the noise generated
by heavy vehicles on public roads. As shown in thesimulated illustration in Fig. 2, noise of a loud vehicle
is much bigger than that of ten quiet vehicles.
2. Progress of Future Road Traffic Noise Abatement
We are implementing the following survey with thetarget of contributing to the policy to convert a loudvehicle to a quiet vehicle.
[Noise of a low-pollution car] It was proved that the noiseof a low-pollution car (medium heavy vehicle class)measured on the test road was almost 1/3 (= -5dB) 2）tothat of average car (Fig. 3).
[Noise of a high noise car] We have measured the noisein several places in the country as to estimate theeffect of loud vehicles. The example presented inFig. 4 shows that values restricted to the top 10% ofloud vehicles achieves the reduction of about 1.3dBof the daily average noise level, which does notinclude sudden big noise in the late-evenings toearly mornings.
[Quiet driving instructions] Reducing the speed andamount of acceleration while driving is expected toreduce the noise and vibration generated, reduce fuelconsumption, reduce and prevent accidents and roadkills, lessen of the deterioration of roads and vehicles.
Although the transport related parties are very aware ofeco-driving, they are actually obliged to follow thespeed of traffic around them. We have a concept that itis required to educate not only the transporters but allother users of the road as well, therefore we would liketo propose posting of banners as an effective way andplan to investigate its effect (Fig.-5)3).
1) Ministry of the Environment: Automobile traffic noise actualstate survey report on fiscal year 2011, MOE web site.
2) YOSHINAGA Hiroshi, SONE Shinri: A study of road traffic
noise reduction by reducing vehicle noise, Environment System
Study Report Presentation Papers, Vol.38th, pp.233-238 (2010).
3) YOSHINAGA Hiroshi, SONE Shinri, KIMURA Keiko,
ANDO Shingo: Enlightenment for drivers as a potential noiseabatement measure, Institute of Noise Control Engineering ofJapan, Papers in presentation, Vol.2011, Fall-time, pp.267-270(2011).

1,000

loud vehicles

Noise emission [mW]1,000
n = 1,148

loud vehicle

100quietvehicle
×10[mW]

Hybrid vehicle- 5 dB≒1/3100(engine noise forrefrigerator)

Average in Japan
CNG vehicle
Hybrid vehicle

1010quiet vehicles

Nosieemsiso
in

20 40 60 80 100 Velocity (km/h)

120406080 100
Velocity [km/h]

120Fig.-1 Noise of the heavy vehicle
on public road．
100NOise level [dB]

1Top10%Fig.-2 Loud vehicle vs. Quietvehicle.

Fig.-3 Noise of medium vehicle on Testroad．

bi g noise i n thel a te‐evening toea rl y morning

908070121806 Time
12Fig.-4 Example of 24 hourmeasurement at site.

Fig.-5 Idea of the banner to encourage quiet driving．
Please drive quietly and softly