Motorists who used to listen to the radio or their favorite tunes on CDs may have a new way to entertain themselves, after engineers in Japan developed a musical road surface. A team from the Hokkaido Industrial Research Institute has built a number of"melody roads,"which use cars as tuning forks to play music as they travel. The concept works by using grooves .They are cut at very specific intervals in the road surface. The melody road uses the spaces between to create different notes. Depending on how far apart the grooves are, a car moving over them will produce a series of high or low notes, and designers are able to create a distinct tune. Paten documents for the design describe it as notches "formed in a road surface so as to play a melody without producing simple sound or rhythm and reproduce melody-like tones". There are three musical strips in central and northern Japan--one of which plays the tune of a Japanese pop song. Reports say the system was invented by Shizuo Shinoda. He scraped some markings into a road with a bulldozer before driving over them and found that they helped to produce all kinds of tones. The _ speed for melody road is 44kph,but people say it is not always easy to get the intended sound. "You need to keep the car windows closed to hear well,"wrote one Japanese blogger."Driving too fast will sound like playing fast forward, while driving around 12mph[20km/h]has a slow-motion effect, making you almost car-sick." In order to hear the music well, you have to  _  .
drive very fast drive slowly open the windows wide keep the windows closed