> The amusing thing about this question is that if you actually have an answer, it reveals more about your biases than it does about the situation and potential solution(s). Various people will chime in about the latest thing that annoys them...whether it is inattentive pedestrians, jaywalkers, pedestrians wearing black at night, drunk drivers, speeders, or people driving cars that are too big and dangerous. But all of them are wrong because there is no discernible root cause.
Causality is usually complex and often complicated. Let's consider another case:
An attentive person without any sensory impairment crossed at a crosswalk in broad daylight and was killed by a sober bicyclist going ten miles an hour[1]. What was the root cause?
All of the same objections apply. If you want an ultimate root cause you need to turn to theology, in which case as a Christian I can say that all death is ultimately caused by sin. While I personally find that to be a philosophically sound position, it isn't especially useful for answering the pragmatic question of how to reduce preventable evils like (some?) pedestrian deaths. My personal bias in this case is to take a pragmatic approach. That means identifying factors that can be changed with a high rate of compliance at a cost that is less than that of the evil being prevented.
Mature safety systems take this into account. As an example, take basic firearms safety[2]: 1) Treat all guns as if they are loaded. 2) Never point a gun at anything you don't want to destroy. 3) Keep your finger off the trigger until ready to shoot. 4) Be sure of your target and what's behind it. In order to negligently discharge a firearm and cause harm, all four of these rules must be disregarded. In this case, even though any number of events from mechanical failure to muscle spasm could have caused the discharge, if someone causes unintentional harm I can say the local root cause was failing to observe the safety rules and hold said person morally responsible[3]. Many other examples of safety systems should come to mind, including relevant to the pedestrian safety scenarios.
[1] One way that this could plausibly happen is that the pedestrian is knocked over and hits his head. Falling and hitting one's head is a surprisingly common way to die.
[2] There are variants, but they all aim to achieve safety in much the same way.
[3] This holds regardless of one's position on civilian ownership of firearms, because police and military personnel are also human and need to follow a safety system.