The issue with vehicles bunching is why I suggested that diesels be banned from the outside lane of 3 or more lane carriageway, that would allow petrol vehicles that are able to do 70mph to pass in the outside lane. I dont think encouraging a switch to petrol is necessarily helpful, except for some people that perhaps want smaller cars that may not suit an electric yet. Electric or alternative fuel should be the encouragement direction for getting rid of small diesels. People with larger diesels or vans have them as they need the grunt to transport larger amounts of stuff, they are less likely to be worried about a reduction in limits, van drivers already being limited on non motorway dual carriageways to 60mph anyway. Perhaps to enforce the speeds diesel vehicles should be required to have limiters put on for 100km/h like busses. With vans small minibuses and small lorries needing to be done first and cars done later. There would likely be a sudden amount of diesel cars on the market where people dont want or have money to install limiters. Likely dealers would be looking to take old diesels for scrapping or exporting to help get them off the road then.c2R wrote: ↑Sat Sep 12, 2020 22:40I'm not sure, and I think that the studies might help with this, whether or not the problem is particularly caused by vehicles in peak time, or how long actually does it take for the NOx to dissipate.lotrjw wrote: ↑Sat Sep 12, 2020 22:26 Perhaps a more revolutionary option is to make all diesel vehicles have a lower mandatory speed compared with other vehicles? That could be made permanent in law too! If say all diesel cars and vans had to travel at 60mph on motorways and dual carriageways and 50mph on single carriageways, just like larger vehicles thats a good start.
Also banning lorries at peak times on motorways and dual carriageways, in fact any road thats outside built up areas, or above 40mph, as has been suggested is a good idea. Reducing them to 50mph top speed on motorways and dual carriageways could also help.
This would make diesel cars unpopular if they are small vehicles, larger ones are good for things like towing so still have use currently, which again is already under reduced speed limits.
In terms of HGV speed limits, they're already limited to 90kmh, which is generally assumed to the be sweet spot in terms of emissions, so it's unlikely that a further reduction would help.
The other issue with different speed limits for different vehicles is that vehicles changing lane to overtake can cause bunching up of vehicles and contribute to phantom jams.
A final aspect is that encouraging a shift back to petrol from diesel will increase carbon emissions. People should be encouraged to select the correct vehicle for the sort of journeys that they typically make. It is also difficult to impose restrictions on hours that hauliers can drive, as freight and distribution is important to the economy. Which brings me back to the planning issues of the local authorities in the area allowing the construction of logistics centres next to the motorway.
I don't think any of the solutions are popular or easy. I would have liked to see this trial accompanied by 80mph trials in rural areas where NOx is less of an issue.
You could be right about HGVs though and I agree about the idea of trialling 80mph limits, or if we switched to metric we could have had 120km/h, in rural areas at the least. Then a ban on building within 500 metres of any 120km/h or 80mph stretches of motorways.