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Tire Talk: Why snow tires don’t wheelie work for Calgary Transit, or other transit authorities

Let’s look on the bright side: Yes, Oct. 2 was one of the worst one-day snowstorms in Calgary history. It was roughly 33 cms, give or take.

While things can change – it’s Calgary, after all – temperatures are expected to be in the positive double digits for most of the last half of the month. Thank goodness.

Still, images of stranded vehicles, snarled traffic and heaps of snow to shovel are forever etched in our minds.

And what about those Calgary Transit buses? Calgary Transit’s Doug Morgan said at one point as many as 80 buses were incapacitated for one reason or another during the morning rush hour that day. Thousands of Calgarians had to make alternate commuting plans.

Inevitably, questions swirled over Calgary Transit’s preparedness, and ultimately their response, for the extreme snow event.

Common question (or slight variation of it) from commuters, reporters and armchair transit critics: Why aren’t Calgary Transit buses equipped with snow tires?

There have been some straightforward answers provided, but we wanted to examine this further, to provide a greater understanding of why this decision’s been made.

Snow tire test runs

At the Oct. 3, emergency operations press conference, Calgary Transit director Doug Morgan was asked if they’d ever done a review of snow tire use on city buses. Answer: Yes, they have.

According to Calgary Transit, roughly 10 years ago they tried an aggressive tread bus tire on the rear-axle of 20 articulated (those accordion-type) buses. They’re the 60-foot models. Calgary Transit also has in its fleet 40-footers and the smaller mini buses.

The testing, according to Transit, didn’t provide measurable improvement to traction or stability. They determined that the extra cost to acquire the tires and the time to make the swap wasn’t worth it.

“We couldn’t find a big enough delta on the performance to make it worth it. We’ve never done a full analysis, but we’ll certainly look at it,” Morgan said at the press conference.

They haven’t done an analysis on the 40-foot buses.

In 2014, Transport Canada did a review on the use of a full set of winter tires on mini-buses and found considerable improvement in traction and stability. But those buses aren’t the problem. Calgary Transit said those buses are rarely affected by a significant snowfall. They rarely get stuck or have traction issues the way the big buses do.

The other reason why it’s not worth it is tire wear, transit officials said.

The supple, pliable type of rubber that gives a winter tire its traction on powdery snow and ice also wears substantially more than a typical all-season tire – especially on dry pavement. Calgary priority one roads, which have the majority of the city’s bus routes, do get cleared (eventually) after a significant snowfall, and, as you’ll see later, quite often the weather improves substantially shortly after these events.

Having it on dry, potentially warmer pavement has tires burning rubber at a much higher rate. Calgary Transit said some of the tires in the test were worn out after 20,000 kilometres.

Calgary Transit’s test was done a decade ago. Halifax Transit, however conducted a similar snow-tire test on five of its articulated buses in 2017.

Originally, a report on snow tire use was commissioned by the Halifax Regional Council (HRC) in response to an Amalgamated Transit Union (ATU) ad in the Metro Halifax newspaper after substantial snowfall and flash freezing in the Halifax area in the winter of 2014/2015. The ad asked for people to join an online petition asking for snow tires to be purchased for buses.

The 2015 report is below. It’s a pretty wide-ranging look at potential tire options and a review of a cross-section of Canadian cities and their best practices. It ends with a recommendation for a pilot project on Halifax Transit buses.

LiveWire Calgary followed up with Halifax Transit to see how the pilot program fared. Different city, similar test with directional snow tires. Same result.

“After the test, we could not definitively conclude that these tires would have less chance of snow-related accidents or incidents,” wrote City of Halifax spokesman, Nick Ritcey, in an email.

He added that their current all-season tire meets all performance measures in snow testing and is severe snow rated.

Tire Talk

Without having one’s eyes gloss over with talk of tread types, mud and snow ratings and tire sizes and such, there’s a few fundamental differences between the performance of snow tires on buses and on passenger cars and trucks. It’s mainly in the tread and the obvious weight differences.

The typical tread on an all-season transit tire is quite deep and quite wide because the tires are much larger than a typical vehicle. According to several online sources, this naturally provides better traction for buses in the case of both mud and snow. So, the difference in performance, if a tire was available, ends up being negligible for larger buses – as shown in both the Halifax and Calgary tests.

That’s if a tire was available. Both the Halifax report and the response from Calgary Transit seems to indicate there’s no snow tire readily available – at least one that meets other transit best-practice specifications.

Most transit tires have a steel sidewall and sidewall protection to prevent sidewall rubbing, according to Calgary Transit. They said sidewall protection is critical due to the likelihood of curb rubbing when they pull up to stops. The close curb stops are necessary to faciliate accessible transit.

“Our tire supplier does not offer a winter tire with these sidewall features and we are not aware of any tire manufacturer that does,” said Calgary Transit spokesman, Stephen Tauro.

Then, of course, you get to cost.

Both Halifax and Calgary noted making the change would add a significant maintenance cost to their budget. Calgary Transit indicated that their current budget for tires was $1.2 million and it would likely double if snow tires were acquired.

Lump in the labour hours for the frequent replacement if they were swapped out prior to and after major snow events, or even just for 1,000 buses each winter and summer season and the cost is substantial.

All things considered, it’s a massive undertaking for what both Calgary and Halifax said was no measurable performance improvement.

Weather factors in

While the questions about snow tires pour in and the commuter rage burbles on social media when major snow flies, we actually haven’t received big snowfalls that often.

Using historical data from calgary.weatherstats.ca, we collated snowfall data over the past five years. It shows that since November 2013, there have only been 19 snow events where the accumulated snowfall was more than 10 centimetres – and that’s total accumulation in events that lasted between one and four days. So, yes, some of these events were strung out over four days to get to that 10-centimetre total.

Furthermore, as you’ll see in the data below, we include the temperature of the three days after these events. Why did we do that? It just shows that in nearly half of these snow events, the weather took a considerable turn for the better, likely resulting in substantial melt – or at least aided in clearing Calgary major roadways.

Oct. 2, 2018 – 32.8 cm (2 Celsius, 3C, 7C)

March 2, 2018 – 13 cm (three days of -10C)

Feb 8, 2018 – 13.2 cm 9 (-11C, -4C, -7C)

Dec 19, 20, 2017 – 15.8 cm (-3C, -9C, -9C)

Nov. 2, 3, 2017 – 12.6 cm (-12, -11, -8)

March 8 to 11, 2017 – 12.8 cm (-12, 9C, 9C)

Feb 3 to 6, 2017 – 24.6 cm (-20C, -14C, -7)

Dec. 23, 24, 2016 – 14.8 cm (-14, -2, 1C)

Jan 2 to 4 – 8.6 cm (-13C, -13C, 8C)

Jan. 6, 2015 – 11.2 cm (8C, -2C, -2C)

Nov. 26 to 29, 2014 – 14.4 cm (-16C, -4C, -2C)

Nov. 9 – 11.4 cm (-7C, -12C, -13C)

Nov. 1, 2 – 16.8 cm (5C, 13C, 7C)

Sept 8 to 10 – 28.2 cm (7C, 9C, 13C)

May 2 to 4, 2014 – 15.6 cm (4C, 3C, 10C)

March 27 to 31, 2014 – 14.8 cm (-1C, 2C, 0C)

Dec 2, 2013 – 14 cm (-14C, -16C, -20C)

Nov. 2, 3, 2013 – 17.1 cm (-4C, 2C, 4C)

We mentioned earlier that the soft-rubber snow tires wear substantially more when not used on snow and ice – and given the weather on many of the days following snow is helping clear Calgary roadways that handle the majority of bus traffic, the tires would either have to be changed to reduce the wear, or they’d have to be replaced more frequently at a much higher cost to Calgary Transit.

Snow safety options

There are other options to help traction when it gets snowy. Including socks.

Vancouver’s Translink piloted Kevlar socks – a mesh wrap for transit tires – on two buses from the Production Way SkyTrain Station up Burnaby Mountain to Simon Fraser University. The cost for two tires on one axle to be fitted with the socks is roughly $250.

Chris Bryan, spokesman for Translink, said the results were positive.

“Drivers reported better traction coming out of bus stops and climbing grades. Compared to using traditional chains, passenger comfort wasn’t compromised and there was no risk of damage to the bus or roads,” he wrote in an email.

Bryan added that these were only limited trials and they’d be looking for more opportunities to test the socks this season.

Translink was also on the hunt for a different solution for snow traction on buses. Snow tires didn’t fit the bill for them either. They dedicated a webpage to it, likely to address frequently asked questions about their use in the transit fleet.

Other options such as cables, studded tires and chains are available, but they create collateral damage on city roads that send long term road replacement costs spiralling. Further, buses are typically slowed down when chains are used and the time to install and remove the chains is excessive.

Calgary Transit’s Doug Morgan said they’d continue to hunt for solutions to deal with these snow events.

For the general operations, the current technology is right, but we’re always looking for other solutions to help us improve our reliability,” Morgan said.