It would now seem that the two new roads will NOT open at the same time.
Two new 'temporary' road signs have appeared on the HRR as you approache the Fieldways roundabout. They advise traffic going to Frome, Westbury and the White Horse Business Park to follow the A361 through Trowbridge (which is not the route signed on the 'permanent' signs).
It is therefore logical that the extension of Leapgate will not open untl after the HRR is in use.
A metrocount device has been installed on Devizes Road. This will monitor traffic flow/speed in the pre-HRR phase.