10 Common TM Mistakes
10 Common Event Traffic Management Mistakes (and How to Avoid Them) This short guide is designed to help event managers understand key compliance risks in temporary traffic management (TTM). Based on real-world experience and aligned with UK regulations, it highlights what often goes wrong — and how to put it right.
9
Wrong Size or Missing Signs
Sign sizes are determined by road speed. Using undersized signs — even by accident — on faster roads makes them illegal and puts drivers at risk.
Higher-speed roads need larger x-heights and bigger sign faces, which aren’t always off-the-shelf.
The size of your sign will depend on the speed and type of road. The height of text on a sign is defined as its x-height (the height of a lowercase x), Chapter 8 lists signs used for roadworks and the appropriate x-heights.
Most road signs which are available to buy off-the-shelf have an x-height of 75mm or 100mm making them suitable for use on single and dual carriageways up to 40/60mph respectively. Roads with a higher speed require larger signs which are not as easy to find, this is not an acceptable excuse and does not make their use legal.
Standard 750mm Regulatory signs are suitable for use on single and dual carriageways up to 40mph. Chapter 8 recommends 900mm sign faces for 50/60mph single carriageways however as stated in "Safety at Streetworks" 750mm is the absolute minimum that can be used on this type of road.
All equipment used on UK roads must meet strict requirements and one of these is quality. The only brand new equipment will be in the "acceptable" range, scratches from being used on the road are inevitable and this is why most signs used are within the "marginal" range. The below images are taken from Chapter 8.
Placement of the incorrect sign size, colour or any factor, along with missing repeater signs (for speed limits and other restrictions) can lead to the nullification of any applied Traffic Order and/or insurance cover
Summary: Sign size must match road speed — but equally important is correct spacing and full presence. Missing signs or incorrect spacing can void your TTRO.
Why This Matters: Signs that are too small, missing, or incorrectly placed lead to confusion, reduce compliance, and can invalidate your TTRO — meaning any driver ignoring it may not be at fault.
Key Regulations:
Chapter 8: x-height and spacing for speed limits and sign repetition
TSRGD: Required sign types for closures and restrictions
Common Issues:
Small signs used on high-speed roads
Missing repeaters or poor spacing
TM plan signed off but not delivered on site
What You Should Do:
Match sign size to road speed (e.g. 900mm+ for 50/60mph)
Ensure all repeaters are in place and spaced per guidance
Audit signage delivery to match approved plan
Event TM Recommends:
Full sign package planning and delivery
Compliance checks to protect your TTRO and legal exposure