The trite expression "Speed Kills" is erroneous.
Speed does not "kill." Differential Speed kills.
Roads that are designed for automobile use, where 99.8% of the usage is by automobiles, are inheriently incompatible with sharing traffic with bikes, streetcars, rickshaws, skateboards, or anything else traveling at a snail's pace with automobiles.
Cyclists are required by law to observe the same rules of the road as automobilies, but many do not. They fail to yield, make improper turns, and disregard traffic signs and lights. Not to mention that their slow speed impedes the entire system.
Bike lanes in cities are few. They cause more trouble for automobile traffic because there is no way to really design them to not impede 99.8% of the other traffic.
Roads that are designed for automobile use, where 99.8% of the usage is by automobiles, are inheriently incompatible with sharing traffic with bikes, streetcars, rickshaws, skateboards, or anything else traveling at a snail's pace with automobiles.And that, my friend, is a description of bad road design.
Towns and cities existed for thousands of years before the automobile came along. Streets and roads accommodated ALL forms of traffic, and the dominant mode was pedestrian. Then came the car, which moved at speeds hazardous to everyone else. So here we are.
Forget bicycles for a moment. Think of pedestrians. People should be able to move around their own neighborhoods safely. People should be able to cross the street safely, and at convenient intervals. Kids should be able to walk or bike to school. The elderly should be able to get around without cars. People should be able to get to their neighborhood parks and pools without driving to them. Roads should not become barriers. Too many suburbanites live in communities that require them to get into their cars to do anything and everything; they've lost sight of how good urban neighborhoods live.
So: it should be part of basic road design that we build sidewalks and ample pedestrian crossings. With minimal upgrades, sidewalks and pedestrian crossings can accommodate bikes as well. On rural roads, have good shoulders; this is proper design for automobiles as well, but it also accommodates pedestrian and bike traffic.
Local situations will vary, but around DC one of the biggest problems is roads on which the shoulders and sidewalks were long ago sacrificed to squeeze in another traffic lane. Planners took the existing sidewalk, spent a bazillion dollars a mile putting in a new car lane, and deemed a replacement sidewalk "too expensive." Planners took a city street in an urban neighborhood and turned it into a high speed commuter sewer, risky to cross even if it's not fenced. This kind of thing kills neighborhoods and produces slums.
Want to put a new arterial road through a residential neighborhood? Ok … provided you have a stoplight and a safe crossing every two blocks, put in a wide sidewalk for neighborhood traffic including pedestrians, bikes, moms with strollers and the joggers and dogwatchers, don't eliminate the on-street parking for local merchants, etc. I.e., don't destroy other people's neighborhoods.
Your commute is too long? Live closer to your job.