I think this one is pretty easy, tho. That article is from 2013 and lists three serious incidents from the same cause. Yes, the carrot is a good motivator for certain behavior, but in this case it's the stick because the solution was known from similar events in other cities and not done. No more arrest vehicles where prisoners are facing sideways. Get them off the streets. From the article I referenced above:

"Schneider was an expert consulted by the ACLU in bringing the Chicago class-action lawsuit. The lead plaintiff was a man who bit off his own lip while rolling about in a police van."

Gray was one "running while black" iincident, but in this case he was resisting (running) most probably because of the same reason people in Philadelphia ran from the police on sight. There's corruption in some police departments or precincts, unprofessional behavior, racist attitudes, cultures of abuse, lack of knowledge of making a proper arrest or the law, loss of moral compass, plus everything that dboh and alternaut spoke of, many factors and each has to be verified as the cause or causes and addressed, in my opinion not lumped together or you never know what really happened in each case and are helpless to prevent it from happening again.

In 1992, Boeing was sued because the cargo doors on a passenger plane opened during flight. It happened before, in 1987. You start with what you know is a definite problem, eliminate that, and go from there. You have to start somewhere...