Agree, 18 MPH is too fast for a DZBL. What then is an appropriate speed?
What triggers the warning lites? The driver beginning to pull on the door handle? That provides maybe less than a second of additional warning time? Are the warning lites on if a driver is in their seat it might be better?
There's a reason that Dutch (and most developed countries except the U.S.) no longer build Door Zone Bike Lanes. They are dangerous in numerous ways; drivers opening doors, drivers pulling out of their space without looking for bicycle riders, drivers pulling in to the bike lane so that they can parallel park, drivers crossing the bike lane to park and squeezing bicycle riders between parked cars and cars driven by inattentive drivers with nowhere to escape if a driver seers in to the DZBL.