Speed cameras are designed to do one thing – issue citations for speeding.
The job of the police officer is to identify a wide array of crimes and issue citations for them, when they observe them.
The incident where a car was tailgating you and the incident where a lorry was creating an unsafe driving situation have absolutely nothing to do with the speeding camera. Both of those situations are the responsibility of a policy officer, if they are alerted to the crime or observe it themselves. You have a valid complaint about the complacency of your local law enforcement, but what does your argument have to do with the speed camera?