Cars making loud scraping noise on speed hump. Solutions?

Fairly quiet residential road in Hackney. There's one speed hump in the middle of the road, outside my flat. About 50% of the cars going over it scrape their under tray and make a loud scraping noise. Any advice on how this could be remedied?

- Would adding one or two more humps on the road make people drive slower and therefore not scrape their cars?

- if it was made higher or lower would that help with scraping?

- would removing it just be better? people seem to just accelerate right up to it, so i dont think it even slows people down. the whole of hackney is 20 anyway.

- are there any other options like a speed cam or LED 20 sign, etc?

cheers!