Trams greener than buses

Novel study shows cities bat­tling smog and diesel en­gines will do well to go back to tramways

The Witness - Wheels - - TRANSPORT - AL­WYN VILJOEN

FEW res­i­dents of Pi­eter­mar­tizburg will have been around when the pub­lic trans­port needs of Scottsville were served by a tramway, which served the sub­urb with large wag­ons and had its ter­mi­nus near today’s tourism of­fice in the cen­tre of town from 1904 to the 1936.

For­mer town plan­ner and Wheels writer Brian Bas­sett said all cities had tram­lines in those years, but these sys­tems fell out favour be­cause ev­ery­one thought crude oil would al­ways be sold for around R15 a bar­rel.

City en­gi­neers then cited stud­ies to show how ex­pen­sive the trams’ elec­tric­ity was com­pared to cheap gaso­line. Ci­ti­zens sup­ported their ar­gu­ments, as ev­ery­one as­pired to be in­de­pen­dent with their own car.

As a re­sult, no one shed a tear when the rails were ripped up and coaches sold for scrap across SA in the mid 1940s.

Now a com­par­i­son of the en­vi­ron­men­tal life­cy­cle im­pacts of tramway and Bus Rapid Trans­port ( BRT) sys­tems points out shows a re­turn to trams, in­stead of buses, are the way to go.

En­vi­ron­men­tal con­sul­tants Car­bone 4 was spon­sored by tram builders Al­stom to con­duct the study. Un­til re­cent- ly, a lack of hard in­dus­try data made it dif­fi­cult to com­pare the long- term en­vi­ron­men­tal per­for­mance of BRTs and tramway sys­tems, but Car­bone 4 said all that changed last year, when Al­stom shared its data on stan­dard tramway sys­tems and its op­ti­mised At­trac­tis in­te­grated tramway sys­tem.

Car­bone 4 is a lead­ing in­de­pen­dent con­sult­ing firm based in Paris spe­cialised in cli­mate- re­silient and low- car­bon strat­egy. Al­stom de­vel­ops and mar­kets com­plete rail sys­tems, equip­ment and ser­vices in 60 coun­tries with 31 000 em­ploy­ees. The re­sult of their study was the world’s first com­par­i­son of end- to- end car­bon foot­print of tramways with those of a range of buses de­ployed in rapid trans­port sys­tems.

Car­bone 4 be­gan by com­par­ing Al­stom’s data to BRT data is­sued by lead­ing French, Euro­pean and in­ter­na­tional in­sti­tu­tions.

The study took into ac­count mul­ti­ple vari­ables, such as the fact that a ful­ly­elec­tric bus with large bat­ter­ies would have less room to carry pas­sen­gers.

It also fac­tored in how of­ten the ve­hi­cles would need to be re­placed — 30 years for a tram and 15 years for a bus — and wear fac­tors, such as bat­tery life­time for elec­tric buses.

The study then an­a­lysed the CO2 emit­ted by the en­ergy used to build, main­tain and re­new the trans­port sys­tem and power the ve­hi­cles.

Re­gard­ing elec­tric­ity, the study took into ac­count the av­er­age elec­tric­ity car­bon fac­tor in Bel­gium, which has a mix of nu­clear, hy­dro and fos­sil fuel sources.

The sen­si­tiv­ity of the re­sults to the emis­sion fac­tor of elec­tric­ity was also as­sessed. Per­haps not sur­pris­ingly, con­sid­er­ing the spon­sor, tramway sys­tems emerged a clear win­ner when it came to sup­port­ing cities in their goals to have cleaner air and cheaper mass trans­port, although Carobon 4 ad­mit con­struct­ing the rails and over­head lines can make the place messy for two years or more.

Con­struc­tion and man­u­fac­tur­ing

Although a bus sys­tem of­fers short- term ad­van­tages dur­ing con­struc­tion and man­u­fac­tur­ing, when mak­ing a tram pro­duces 400 tons of CO2 com­pare to mak­ing a diesel bus, which emits only 30 tons of CO2, the tramway sys­tem is a clear long- term win­ner, with much lower over­all life­time emis­sions, thanks to its bet­ter oper­a­tion and main­te­nance per­for­mance and the longer life­time of the trams. Due mainly to the com­bus­tion of diesel to power the bus, a diesel BRT’s to­tal life­time emis­sions are more than twice as high as the ones of a tramway sys­tem.

For the same rea­son, a plug- in hy­brid BRT sys­tem emits about 30% more green­house gas ( GHG) than a tramway sys­tem over its life­time.

The BRT sys­tem also uses more elec­tric­ity than the tramway one with a sim­i­lar trans­port ca­pac­ity. Even a fully elec­tric BRT sys­tem has 17% higher life­time emis­sions than a tramway sys­tem, since a city would need to op­er­ate a large fleet of buses to achieve the same trans­port ca­pac­ity as 20 trams, re­sult­ing in 3,6 times more kilo­me­tres trav­elled by a bus an­nu­ally.

Be­cause BRT in­fras­truc­ture is lighter dur­ing the ini­tial con­struc­tion phase, its as­so­ci­ated emis­sions would be 2,2 times lower than for a tramway.

If a city can use ex­ist­ing road in­fras­truc­ture as a ba­sis to build a BRT sys­tem, it would how­ever need to re­in­force it for heavy traf­fic and build stops and other as­so­ci­ated el­e­ments.

Im­pact of en­ergy mix

Elec­tric­ity pro­duc­tion ac­counts for more than 40% of global fos­sil CO2 emis­sions. Since tramways are pow­ered solely by elec­tric­ity, how does the elec­tric­ity mix in­flu­ence the car­bon foot­print ad­van­tage of tramway sys­tems?

Even in a worst- case sce­nario in which the elec­tric­ity emis­sion fac­tor is around 0,800 kg CO2 per kWh, as in China, all other as­sump­tions re­main­ing the same, the tramway’s car­bon foot­print re­mains lower on a 30- year life­time than a diesel, hy­brid or elec­tric BRT sys­tem.

Car­bone 4 also pre­dict the elec­tric­ity emis­sion fac­tors will sig­nif­i­cantly de­crease in the com­ing years, thanks to the cur­rent de­vel­op­ments in the fields of re­new­able en­ergy, which will re­duce fur­ther the foot­print of elec­tri­cal modes.

This ranges from new uses of sil­ica which in­creases sev­eral 1 000 times the heat of heavy salts in so­lar en­ergy cap­tur­ing sys­tems, to Tesla and So­lar City merg­ing to form one com­pany, to Toy­ota mak­ing a fuel cell car that dou­bles as a mo­bile power gen­er­a­tor.

Af­ter do­ing the study, Al­stom had to get in a punt for its prod­uct, the At­trac­tis a tram ser­vice.

Al­to­gether, over a 30- year life­time, At­trac­tis said in a state­ment its tramway sys­tem will emit 57% less GHG than a diesel bus sys­tem, 32% less than a plugin hy­brid, and 23% less than fully- elec­tric bus sys­tem such as BYD or Volvo uses. Al­stom said a 12 km long At­trac­tis tram sys­tem can be fully op­er­a­tional within 30 months.

PHOTO: FAD. CO. ZA- AL­STOM

LEFT: This pic­ture of Old Faith­ful, Dur­ban’s last elec­tric tram, was taken on Au­gust 2, 1948 in Mus­grave Road out­side Jame­son Park. RIGHT: A mod­ern- day elec­tric tram in Brus­sels, Bel­gium.

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