LRT riders had to walk along tracks during breakdowns including in the tunnel

Six train failures in back-to-back rush hours have caused commuting havoc in Ottawa, forcing Confederation Line passengers to be evacuated from their trains and in one case, requiring them to walk along the tracks in the downtown tunnel.

The extent of the chaoswas confirmed Thursday morning at an OC Transpo news conference.

OC Transpo boss John Manconi told reporters that customers don't "want to hear the excuses, the rationale, the technical nuts and bolts, they want one thing service."

But for thoseinterested in what's gone wrong this time with the $2.1-billion Confederation Line, here arethe nuts and bolts.

4 trains down Wednesday

At 4 p.m. Wednesday, a cablethat's part of the support system forthe overhead electrical cable came loose and broke just east of St-Laurent station.

Rideau Transit Group (RTG) CEO Peter Lauch, who also attended the Thursday news conference, said he doesn't know why the cable broke, but it didn't appear to beweather-related.

The breakage immobilized one train. Riders were told to get off, and they had to walkalong the track to St-Laurent station.

A little more than an hour later, around 5:20 p.m., the repair workended up immobilizing awestboundtrain just east of Tremblay station. In this case, since the train was farther away from the station, another train pulled up beside it to ferry passengers to the next station.

Those passengers had to walk across the rail bed to the working train.

Troy Charter, OC Transpo's direction of operations, saidthe "fluid situation" resulted in "a challenge in communicating real-time information to our customers."

Two more unrelated problems then occurred: a westboundtrain at uOttawa station lost power around 7:20 p.m., and less than an hour later, an eastbound train had a door issue at Bayviewstation.

In four hours, four trains were taken out of service.

Only 5 trains at one point

The overhead cable system was fixed after midnight, but there were additional power issues overnight in the maintenance yard overnight.

Those issues, plus the fact three trains are in the shop for "heavy maintenance," meant the morning rush hour began with only ninetrains in service.

That number first fell to seven, and at some points Thursday day all the way to five the lowest level during the five months the Confederation Line has been in operation.

At 5:30 a.m., a light rail vehicle lost power just east of Rideau station, and the train could not continue. Customers were asked to disembark, and had to walk about alongside the track in the tunnel about 15 metres.

An hour later, another power issue stopped a westbound train at Tremblay station. It wasn't until 8 a.m. that both these trains were removed and trains were able to run the length of the 12.5-kilometre track.

Arc flashes

The power loss issues appear to be related to arc flashes, which we heard aboutearlier this month. The arc flash likely stems from a buildup ofcarbon and salt on the roof of the trains, coupled with small cracks in the inductorswhich filter electrical power from the overhead cable to the train.

• CBC Explains: What's an 'arcing flash,' and why is it ruining your commute?

RTM'sshort-term hacks to address the issueinclude cleaning the carbon and salt off the roofsand building a "chimney" around the inductors to protect them from the weather.

Lauch said RTG will only send out trains that have the new chimneys installed, but only 19 of the 34 light rail cars there are two cars per train have been modified so far.

Hesaid it will be more than a week before the rest of the fleet has the inductor covers installed.

Only seven trains have been made available for Thursday's afternoon rush hour.