If the ghosts of people who died in the road began to spook drivers and cause more accidents, you would see a rapid spike of mortality in the short term, follow

If the ghosts of people who died in the road began to spook drivers and cause more accidents, you would see a rapid spike of mortality in the short term, followed maybe by change of behavior where ~90% of traffic is composed of professional bus/truck drivers that are hardened and not easily affected by ghosts.