When the DfT’s Traffic Signs Technical Working Party last met in December 2019, this was on the agenda. DfT indicated that the review would not be in any detail, and was little more than addressing the question, “Do we still need traffic signs regulations?” So the answer is pretty obvious: “yes, we do.”
Government writes this 5-year review clause as standard into almost all regulations, as they are regarded in general as burdensome things restricting what you can do or imposing possibly unnecessary tasks. TSRGD is of course largely the opposite: it is enabling and giving legality to things that might not otherwise be permissible, and also providing much needed consistency.
So in this case, it is the proverbial ‘box ticking’ exercise!