Idea HN: Bomb proof bins

The solutions that you see in the UK after various terrorist bombings are:

1) Bins get removed. If you look at chunks of London which are high-risk "targets" you will see a lack of public waste-bins.

2) Bins get changed to be less useful for hiding devices in. For example the UK rail stations often have bins that are just a transparent plastic bag hanging from a hoop. Any large/heavy device would be obvious quite quickly.

Both of these have associated costs of course (rubbish on the street and more frequent changing of bins respectively).

How about weight though? I imagine most bombs are considerably heavier than normal refuse. Could we add scales to bins and notify authorities that it should be examined if the weight suddenly increases by 2+ standard deviations, say.

I suppose this could be worked around by dropping explosive material piecemeal into the bin so this would have to be paired with an effective surveillance system to pick up on this behaviour.