There is a web site where you can report incidents of litter dropped from vehicles. You may or may not think this is a good idea, you may or may not think it will have any effect. If you answer no, then just ignore this posting, but if you do want to report such incidents, go to www.keepbritaintidy.org where there is a link to allow you to make a report. From the statement on their site:
Geoff
By using this site to report littering whether from a car, bus, lorry, minibus, motorcycle or van you will join our petition and be amongst an ever growing number of people throughout England wanting to put an end to the car litter problem.
Every time you see someone littering, help us do something about it by inputting the incident to our site. By providing us with the detail of the littering offence you will help us gather evidence to raise the importance of this issue throughout England. We need as many of your reports as possible to show at the highest level just how seriously so many of you take the issue.
Geoff