The ‘smart’ bit is only a small element of what is basically essential maintenance and upgrades to existing motorways, carried-out at huge cost because the road need to be kept live.
The schemes take so long because there is a lot to do. The usual thing where there is land available is to build a new hard shoulder. This involves new embankments, cuttings, soil reinforcement and extending the width of all the under bridges. The new hard shoulder is built to full-running lane standard. Then they need to dig out the old hard shoulder to full depth and rebuild this to become lane 1. Dependant on ground conditions, this can be two metres deep. Once that’s done they can resurface old lane 1 / new lane 2. Then job is half done, move the traffic on to HS, L1, L2 and start building in the centre. Rip-out the existing central reservation, replace the drainage, foundations for the concrete safety barrier, foundations for gantries, extruded concrete surface water channels to come or both sides, then extrude concrete safety barrier itself. Re-tarmac lanes 3, 4 and edge. White line everything, install cats eyes, cut traffic detection loops, install signs, electronic message boards, test and commission the road with safety inspections etc. Whilst that’s going on, there’s all the other associated stuff that gets slotted in - NRTS fibre network, street lighting, emergency phones, road restraint barriers, fences, landscaping, bridge column strengthening, access footpaths & steps, bridge bearing replacements, cctv cameras, petrol interceptors, attenuation ponds, building and removing all temporary sites, compounds and access roads. Everything done whilst not killing any birds. Every one of these activities has huge quantities. On the scheme I worked on J25-28 M1, there was over 100,000m of rib line (rumble strip) and 700,000 trees.
Smart or not, these critical roads needed the upgrade of the basic civils. Once complete, they are fixed for a good few years.
Wait until they seriously start on replacing rather than repairing the elevated sections of M6 & M5 in Birmingham. That could take a decade or more working in the same manner.