By Grantley Martelly, Managing Director of Safety and Security
Chris Parrott, Superintendent of Metro Transit Vehicle Maintenance
King County Metro operates the nation’s second-largest trolley fleet, and we are committed to preserving our long safety record, for our customers and our employees. Last year we introduced our first new trolley buses in 30 years.
It is not unusual for a new fleet to come with unexpected challenges. Metro has experienced two issues with the New Flyer trolley fleet. One is a mechanical problem that causes the trolley poles to disconnect unexpectedly, temporarily cutting off electric power to the bus. Secondly, there were two incidents in which mechanics received an electric shock while performing routine inspections beneath these coaches at the bus base.
At no time were passengers on these buses at risk. Metro has since taken steps to improve training and workplace safety for vehicle maintenance staff in response to these incidents.
As for the dewirements, we expect to retrofit the entire fleet with stronger springs in the next two months, along with a software update.
Trolley poles dewiring
Customers on our trolley routes may have noticed the poles increasingly disconnecting from the overhead wire while the bus is in motion. While this happens occasionally every day with our older trolley buses, it became increasingly frequent for drivers on the newer trolleys a few months after they began service – sometimes as many as 20 times in one day. Routes 3, 7, and 70 have seen some of the most dewirements.
In spring 2016, Metro notified the manufacturer, New Flyer, and the trolley pole system manufacturer, Vossloh-Kiepe, asking them to identify solutions to the problem.
After testing the manufacturer’s solutions, we began implementing two fixes for these problems and we are already seeing improvements.
First, we addressed a software issue that made it more likely for poles to disconnect. Testing and observation revealed the system was programmed in a way that made it overly-sensitive, causing the poles to automatically retract unnecessarily if the bus traveled outside a certain range from the wires, or hit potholes or an uneven road surface. Under the warranty, the manufacturer provided us with a software update that is better calibrated to our environment, and we recently installed it. We are already seeing improvements.
Secondly, each trolley pole system is equipped with a set of four industrial strength springs, which hold the poles up against the overhead electric wires. Over time, we could see that the original springs on these new coaches were unable to maintain enough pressure to keep the poles in place on the wires, and the poles would intermittently disconnect. Under warranty, the manufacturer tested stronger springs, and they appeared perform satisfactorily during testing.
Yesterday, Oct. 26, Metro received the first major shipment of new springs from the manufacturer, and our staff is working to install them. Depending on the pace of shipments from the manufacturer and continued good performance, we expect to retrofit our entire fleet by the end of the year.
Electrical shocks under the bus on two occasions
On May 9, a mechanic inspecting one of the trolley buses leaned against a metal rail while opening a valve underneath the bus, which subjected him to a charge of 300 volts, according to a preliminary report. The trolley’s power system was connected to overhead wires at the time. It is unclear how many amps – the rate of flow of the electric charge – to which he was exposed. The mechanic received medical attention prior to returning to work.
During our internal safety investigation, it was discovered the “hot coach detector” had been disconnected on this one bus at the time of this incident. Our trolleys are equipped with these detectors, which are designed to alert operators or maintenance staff if stray electric current is present anywhere on the bus. If a hot coach incident happens while the bus is in service, the detector automatically disconnects and retracts the power poles and shuts off power to the bus. Passengers were in no danger of coming in contact with stray electric current thanks to the design of these fiberglass-shell coaches, where all metal components inside the bus are isolated from metal where stray current could go. Other components outside the bus, like bike racks and ramp lifts, also are isolated from any possible stray electric current to protect the public.
After this incident, our fleet engineers immediately inspected Metro’s entire new trolley fleet and confirmed that hot coach detectors were functioning in all other buses. Metro worked with the manufacturer to install a software update across the entire new trolley fleet so that an additional warning is triggered if the hot coach detector becomes disabled.
On August 31, a second mechanic received an electric shock while inspecting a different bus from underneath. That mechanic also opened a valve and touched a steel beam when the shock – estimated at 25 volts – occurred. According to our preliminary investigation, the hot coach detector was working properly but the employee did not check it prior to performing maintenance.
Metro has since taken steps to improve training and workplace safety for vehicle maintenance staff in response to these incidents. You can find out more about that plan online. We are detailing these actions in a response to the state Department of Labor and Industries, which investigated one of the incidents and fined Metro $10,800 for two safety violations related to training and documentation. We report to L&I prior to a Nov. 1 deadline on how we have remedied the violations.
These were isolated incidents. Metro has no record of any passengers or customers ever being shocked while on a bus. No passengers reported being shocked before or after either of the hot coach incidents. None of our operators reported a problem with this bus. In addition, Metro operators are trained on safety procedures in the event of a hot coach incident while the bus is in service to ensure the public is never at risk.
As of October 14, Metro has put 152 of 174 new trolleys into service. These are state-of-the-art trolleys, a mix of 40- and 60-foot-long buses, equipped with low floors for easy boarding, air conditioning and backup battery power for traveling off-wire.
Metro has safely operated electric trolleys for a total of more than 40 years, and we are committed to keeping safe and reliable transit service as our top priority.