Milled rumble strips is one way to attract the drivers’ attention when they involuntarily are about to leave the lane. The rumble strips provide both internal and external noise but also vibrations in the vehicle. The overall aim of this work is to elucidate the effects and consequences of the use of intermittent milled rumble strips compared to sinus milled rumble strips in the center of the road. The comparison take into account; external noise, internal noise, vibrations, damage to the road surface and the price. However, due to lack of data, vibrations and price issues are excluded here. The work is based on documentation of lessons learned in Sweden, Denmark, Norway and Finland. In Denmark, Norway and Sweden, measurements were made of the maximum external noises. There were major variations in results for both intermittent rumble strips and sinus rumble strips. The results show that the intermittent rumble strips provide an increase of external noise on the 2—8 dB (A). The corresponding figure for the sinus rumble strip is 0.0 to 4 dB (A). Further, it is found that the sinus rumble strips provide more low frequency noise (30—40Hz) compare to the intermittent rumble strips (60—160 Hz). Maximum noise from intermittent rumble strips are obtained around 80—90 km/h, and at 90 km/h the threshold for noise for those living close to the road is 90—140 meters. It is not known at what speed the sinus rumble strip provide the maximum noise. There is reason to believe that what is perceived as disturbing is not only related to the maximum noise but rather to fact that the sound deviates from the traffic noise monotonous sound. The rumble strip sound is more low frequency and not continuously. Regarding the internal noise most studies have focused on passenger cars and an increase in internal noise when driving on intermittent rumble strips varies between 13—17 dB (A). For the sinus rumble strip the corresponding values are 1—6 dB (A). If the level obtained for the sinus rumble strip is sufficient in order to attract the driver's attention is as far as we know not evaluated. However, results from simulator studies show that even low levels of internal noise is helpful for drivers who are about to leave the lane due to sleepiness. The sinus rumble strips provide not only noise but also vibrations. What the most important component to attract attention is, is not known, but most truly the vibrations create an important contributing effect. There are almost no studies available on the effects regarding drivers of trucks and buses. The coating quality is one aspect to consider and experience shows that the less areas milled, the less damage on the coating. Furthermore, there is a recommendation not to mill on surface thinner than 25 mm. The majority of tests have been on the shoulder and not in the center of the road. Evaluations from Denmark and Norway combine the sinus rumble strips with the lane marking, the so called drip flex (coating mass dropped into points near each other in a line formation) and the top of the sinus rumble strip is a bit under the surface level. This is done to protect the sinus rumble strip and the coating. (Author/publisher)
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