As from yesterday big lorries (trucks) have been granted a higher speed limit so there may be a little less congestion behind them.
That said, they are still 10 mph slower than cars -
Cars on a motorway 70 mph, trucks 60
Cars on a dual carriageway 70, trucks 60
Cars on a single carriageway 60, trucks 50
And lower for all in built up areas, in areas with streetlights unless posted otherwise, and as posted.
I would have given this for the UK, but we still don't have a UK forum here despite the failure of the Scottish referendum last year.