Google and Apple have agreed to amend their audio prompts after a double fatal crash appeared to have been caused by incorrect directions from a sat-nav.
A coroner warned tech companies, including TomTom, to a risk of future deaths after a woman drove the wrong way onto the A5 near Milton Keynes.
Sean Cummings, assistant coroner, said Tracey Haybittle, 58, and Amal Mohamed Ahmed, 38, both died in a head-on collision after Ms Ahmed appeared to have followed "audio directions from her sat-nav application".
TomTom said recent changes had been made to its verbal instructions. Apple and Google hoped changes to their audio prompts would provide clearer guidance.