From driving over speed 'blister' humps. If you centre the car and straddle these humps to minimise the shock you tear up the inner shoulders of the tyres on the sloping sides of the humps. This type of hump is ridiculous. If drivers straddle them there is no need to slow down but the drivers wreck their tyres and could suffer a blowout on the motorway. The only people who benefit are the contractors who instal them.