That&#x27;s been done, in the form of magnets driven into holes punched in the pavement.  Early systems just followed the magnets, but today, they&#x27;d just be used as an additional hint.  It&#x27;s quite possible that we&#x27;ll see those in areas with heavy snow.  Volvo has been testing this.[1]  One of Volvo&#x27;s arguments is that magnets are also useful for snowplow guidance.  Heavy plows often chew up the infrastructure when snow is heavy enough that the road isn&#x27;t visible. In some areas, poles are placed alongside roads so the plow drivers can tell where they&#x27;re supposed to be plowing. Sometimes this works.<p>[1] <a href="http:&#x2F;&#x2F;www.gizmag.com&#x2F;volvo-road-magents-autonomous-cars&#x2F;31172&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.gizmag.com&#x2F;volvo-road-magents-autonomous-cars&#x2F;311...</a>