Wherever possible, businesses should encourage working from home or greater choice and flexibiliy in hours. Whilst that isn't possible for many jobs, if there was greater uptake in those jobs where it is possible then it would remove a % of cars from the roads during rush hour, leaving them clearer for those that have to use them.
Nice idea, but there are limits to what can be done. For example, people who drop kids off at school in the morning have pretty restricted options for their working hours as they then need to collect them from school at the end of the day, so their "commute" is pretty well fixed for during school hours, as they can't shift their working day forwards or backwards as then they'll not be able to do the school runs before/after.
Same with people who are customer facing and where staff are needed to be in work within normal working hours as expected by the customers who expect the staff to be in at 10am and 3pm, but not at 8am or 8pm.
Even "back office" staff who don't usually see customers, are still expected to be at work during the core working hours, when other staff may require support etc.
You can realistically only "flex" the working day by an hour or so before/after the core 9-5 hours, and most big firms already do that. The "rush hour" would be a lot worse if there wasn't already so much flexitime and flexed working day.
I think what really needs to happen is to push firms to reverse their "centralisation". Get them back to several local/regional offices rather than concentrate themselves in 1 or 2 super-sized sites. That will spread out their workers over several different sites/towns/cities and reduce the impact of enormous numbers of people trying to get to the same place at the same time, when the majority of the country has plenty of spare capacity in terms of roads, railway lines, land, etc.
I'd love to see some government initiatives to encourage firms to employ more locally, such as reduced national insurance for staff living within say 5/10 miles of the workplace site. That would really make firms sit up and think about relocating or opening local/regional sites.