It was also the intention that the new MS matrix signal would be installed on gantries above individual lanes, and even embedded in direction signs, where they would show arrows pointing in different directions to dynamically change the route that traffic was to follow to different destinations. This wasn't ever tried out, but those 50 symbols included arrows pointing in every conceivable direction to allow for it.
In parallel with the new signals, the new National Motorway Control System was set up in 1970, providing a coordinated way of controlling them. The NMCS had two control centres, one at Coleshill and one at Westhoughton, which normally each looked after one half of England but which were each capable of managing the entire motorway network if the other was incapacitated.
Before long every mile of motorway in England was equipped with MS equipment and the temporary Motorwarn system could finally be decommissioned, years after its sell-by date.
The MS is, remarkably, still with us and still routinely installed today. There are few major motorways where they are the only signals, but — on quieter routes, sliproads and, most often, as individual lane signals on overhead gantries — they are still going strong, more than forty years after they were first installed on the Severn Bridge. They received some upgrades in 1989, with the introduction of new matrix lights to form a red "X", reinforcing the instruction to stop given by flashing red lamps, and the replacement of the "road clear" symbol (which was wide open to litigation if the road proved not to be completely clear) with the new "End" indication.
In Scotland and Wales, however, trunk roads had been devolved for some time, and the new Motorway Signal was not adopted. Both now have matrix signals either very similar to, or identical to, those described here and used in England, but for a long time that wasn't the case. Remarkably, Scotland never rolled out the MS at all, and to this day in rural areas still uses a permanent installation of the Motorwarn signal.
Just like a normal road sign
The MS and NMCS reigned supreme for more than twenty years, some of the most advanced variable message signs in the world connected to a revolutionary national control system. In 1991, NMCS2 was set up, forming a new, more modern national control network, with the motorways around Manchester the first to benefit from the new technology. Initially thirty control centres nationwide looked after the system, but now there are just seven regional centres. It went hand in hand with the MS2, a new type of matrix display that could show longer written messages in two rows of twelve characters, and bringing us into the modern era of variable message signs. They are typically mounted on the left side of gantries with individual MS lane signals and supplement the individual lane symbols. The introduction of MS2 caused some naming confusion and the MS is, now, usually called the MS1.
The MS3 followed in 1999, normally mounted on its own cantilever on the motorway verge, with either a display of two rows of 16 characters or three rows of 18.
Remarkably, though, there was no more sophisticated way to show a pictorial symbol than the 1968-designed MS1 until 2008, when the Highways Agency announced that the MS4 was ready for use: a large-panel display capable of showing two colours, any number of high-definition pictograms, and mixed-case text in regulation Transport lettering just like a normal road sign.