A Temporary Traffic Order (TTO) is a form of legal instrument used by highway authorities to implement traffic management controls on their roads - the power to do so lies with Section 14 of the Road Traffic Regulation Act (1984).
That Act explicitly specifies that TTOs are to be used for 'works' (roadworks) on the road, or for dealing with immediate danger, or for litter clearing, and cleaning.
As might be expected from the name, Temporary Traffic Orders have a maximum duration of 18 months, except for works that cannot be completed within that time period. They are not expected to be a precursor to a permenent Traffic Regulation Order (TRO) - that means that if the changes are intended to be kept, at the end of the 18 month period (or before it) the TTO has to withdrawn and replaced by a new, permanent TRO.
For this reason, Experimental Traffic Orders (ETOs) are preferable for the rapid implementation of changes to benefit walking and cycling, as they can be implemented quickly (with no prior consultation), followed by a six month objection period (forming the consulation), and can then lead directly to a permanent scheme, without a further (new) traffic order. A decision on whether to make an ETO scheme permanent has to be made within 18 months.