While it is important for cars to have speedometers so that drivers can learn to judge their speed, with a little bit of caution, a journey during which the speedometer fails can be completed both safely and within speed limits.
On the Volvo 240, the analog speedometer tends to get sticky after you've done a couple hundred thousand miles. Sometimes it will reset if you just hit the dash hard enough, sometimes you just have to guess the speed based on the RPM and gear and experience.
