=+38. Stop signs. Highway safety engineers test new road signs, hoping that increased reflectivity will make them more visible to drivers. Volunteers drive through a test M12_SHAR8696_03_SE_C12.indd 419 14/07/14 7:30 AM 420 CHAPTER 12 More about Tests and Intervals course with several of the new- and old-style signs and rate which kind shows up the best.