Discussion on Papers 1–2

DR QUARMBY

In introducing the discussion session, I would particularly draw attention to the debate about the dual carriageways versus high standard single carriageway roads. I would argue that taking full advantage of high standard single carriageway roads requires a degree of opportunistic driving which HGVs, with their low acceleration characteristics, may just not be able to achieve. By contrast, it is the predictability of journey times which dual carriageway roads allow HGVs to achieve that gives the real value, as journey planning requires a degree of certainty - the 90 percentile journey time. While good average speeds may be achieved on standard single carriageway roads, the lower predictability makes them of less value to HGVs. My question is this - does the choice of either a dual two-lane or a high standard single carriageway road reflect these factors?