This probably isn’t going to happen any time soon. The idiots who demand the “right” to drive as fast as they like, unregulated and unmonitored, are not going to let any automated system take control of their car — even to save their own lives, let alone anyone else’s.
Still, there is a DFT report about Intelligent Speed Adaptation here. The preamble describes Intelligent Speed Adaptation like this:
Intelligent Speed Adaptation (ISA) is a system that provides, within the vehicle, information on the speed limit for the road currently being travelled on. That information can be used to display the current speed limit inside the vehicle and warn the driver when he or she is speeding (i.e. Advisory ISA); it can be linked to the vehicle engine and perhaps brakes to curtail speed to the speed limit for the road while allowing the driver to override the system (i.e. Voluntary ISA); or it can be linked to engine and brakes without the possibility of an override (i.e. Mandatory or Non-Overridable ISA).
The DFT reports describe technical trials and user attitudes and behaviour.
Adaptive cruise control is, like a lot of this stuff, more aimed at driver safety and/or comfort, than sustainability. Still, it might lead to better “driving”, if only because automated systems might make better decisions about how often they need to accelerate and brake. Here is a widget that you can buy to go in your car.
Finally, the various projects for driverless cars deserve a mention, though I doubt that this is likely to have any impact on the overall sustainability of personal mobility any time ever.
There are some plans to trial driverless cars in Masdar, the sustainable city planned for Abu Dhabi. There have been some trials in Derby too; and Advanced Transport Systems Ltd, a specialist company, has a website with lots of reports, case studies, and some admittedly rather cool pictures. My personal favourite is still the JohnnyCab from “Total Recall” though.