. THESIS
A COMPARISON OF THE COSTS OF OPERATION OF THE MOTOR BUS, BIR.i.'IBY
SAFETY CAR Ai.'1D TROLLEY BUS ON THE LOCAL TRA.i.~SPORTATION
ROUTES IN PASADENA
Douglas A. Stromeoe
Prepared as a Partial Fulfillment of the Requirements for the
Degree of Bachelor of Science in
Civil Engineering
CALIFORNIA INSTITUTE OF TECHNOLOGY 192, A COMPARISON OF THE COSTS OF OPERATION OF THE MOTOR BUS, BIRNEY SAFETY CAR AND TROLLEY BUS ON THE LOCAL TRANSPom:ATION ROU'.rES IN PASADENA
.!.._-:_INTRODUCTION
With the installation by the Pacific Electri c Rail- way of a bus system in Pasadena to supplant most of its trolley lines, the problem of the comparison of the costs of the two systems naturally presented itself. The study he1•e under- talcen was 01.. iginally started as just a comparison of the motor bus and Birney Safety Car,but as the wo:t>k progressed it seemed advisable to include the trolley bus as well - a method of transpor•tation that is comparatively new as far as development is concerned, but which seems to be finding increasing favor in the East. II - SCOPE OF STUDY
The Pacific Electric Railway proposes to establish nine bus routes, lettered from A to I, supplanting existing rail routes and extending to other regions not hitherto served. Three of the rail routes will be retained, numbered in this study Routes, 1, 2 and 3, and upon these three routes Birney Safety Cars are to be operated. This makes a total of twelve routes and each of these twelve is here considered with respect to all three systems of transportation. It might be well to mention here one of the ad vantages of the bus system - that of being able to experiment on a certain route to determine whether it would be -I- profitable, before any expensive equipment is installed, such as rails and trolley wires. In this way, shifts may be made from time to time in the streets .operated upon, until the best route is .found. Thus an initial bus route, such as those here presented, may be entirely different after a few months of operation. However, in the present study it is assumed that these routes as selected by the Pacific Electric under advisement of the City of Pasadena represent the best routes that could be picked and that any .future rail development would be along the same streets. A rail route, however, would per haps be somewhat sho1.. ter than a bus line se1.,ving the same territory due to the elimination of loops, and allowance has been made .fo1.. such a contingency.
Anothe1.. consideration is that in the case o.f t·wo 01• three rail lines using the same street (as Colorado Street) for a portion o.f their distances, the entire initial cost of the rails on the portion common to two or more lines should not be charged to each. To do so, hmvever, is on the side of saf'ety. The Pasadena Short Line and the Oak Knoll are inter urbans and although they handle local traffic i n Pasadena they must be run anyhow, and a study of their operation as relating to local traffic need not be considered here. The lengths of the rail lines were found by scaling from a map and the lengths or the bus lines were taken :from
- 2 - Pacific Electric data. It is assumed that the ave!'age speed of buses will be nine miles per hour and that of the cars and trolley buses ten miles. This is due to the fa.ct that the buses must draw up to the curb to discharge and take on passenger•s, and that the electric motored vehicle will have a little faster pick-up than the motor bus. The comparison is made on the basis of equivalent service by each system. The short or rush-hour headway is assumed for five hours each day, with double that headway (or half the service) for the remaining fifteen hours or the twenty hours daily oper•ation. (See data sheets).
III - UNIT COSTS An examination of the various items affecting the cost of operation of a bus or car show that some or these items are constant regardless of the number of car miles operated, while others vary with the number of miles of travel. Because of this fact the best way to compare costs is by a study of' curves showing the variation for each mode of trans portation, of the cost per car mile with respect to the total car miles operated. Since the nurnbe1• of car miles operated is based on the headway maintained, a knowledge of the demands of service will make these curves of value in showing just vn1ich system would be cheapest in operation on a given route -
- 3 - not only at present but also when increased service will in- crease the car miles operated. In compiling a list of expenses of operation two authorities were used - Thirlwall in "Bus Transportation" (Sept.1922) and the Interstate Railroad Commission figures on the comparison of costs of operation of several trucks tested under its supervision. vi/here sufficient data was lacking ap proximations were made of some of the costs. This is war- ranted a.s long as these figures remain comparable for the three systems of service. The fixed costs in dollars per car mile are: BIRNEY TROLLEY MOTOR UAR BUS BUS 1. Power (@rp.015 per K. VJ .Hr.cost $ .025 per car mile) ;jj; .0250 1iiP~ • 0250 2. Gasoline (7.9 mi.per ga.l.@20¢) $ .0253
3. Lubrice.nts ( 400 11 II If @ 70¢') .0006 .0006 .0018
4. Tires ( ~~ 300 per six with 12000 mile life) .016'7 .0167
5. Repairs .01'70 .0170 .0350 6. Maintenance of Way .0180 7. Drivers• Wages .0289 .0289 .0289 8. Superintendence .0035 .0035 .0022
9. Garage .0029 (Thirlwall gives costs per mile of track for car ba.rns,substations, etc.-See formulae below) IO.Insurance - 4 - BIRN:B~Y TROLLEY MOTOR GAR BUS BUS
(a} Fire & Theft ~~ .0024 ;}.0024 '"'~p. 0024 {b) Collision .0026 .0026 .0026 ( c) Property Damage ~0014 .0014 .0014 (d) Liability .0112 .0112 .0112 11. Admin:tstration .0039 .0039 .0025
12. Dep1~eciation .0150 .0150 .0400
Bus: Initial Cost !~~8, 000' life 200,000 miles. Birney Car & Trolley Bus: Initial Cost ~·~ 6,000, life 400,000 miles. 13. Miscellaneous (3%) .0039 .0039 .. 0052
TOTAL ~~.1334 ~~ .1321 $, .1781
The costs here tabulated are incorporated in the fornmlae deduced below.
IV - DEVELOPMENT OF FORMULAE
A. FOR MOTOR BUS Let. b • number of buses required. c = total cost per car mile in dollars. h = maximun headway. 1 = one way length or route. m a number of bus miles operated per year. 1. Interest on Bus Investment .06 x 8000 = $ 480 interest per bus per year Then~ • cost pe:r• bus mile. 2. Interest on garage investment Investment = $ 1000 per bus Inte rest = .06 x 1000 = $60 per bus per year. rm:ien 60b = cost per bus mile J. .L ""'1'!'F-' - 5 - 3. Garage Depreciation. Garage life assumed as fifty years 1000 • $20 cost per bus per year ~ Then ~ = cost per bus mile. m The total cost ner bus mile for the Motor Bus • c• • 1781 * 4~0b- + 6~o + 2~b = .1781 + 5~00
B. FOH BIRNEY CAR AND TROLLEY BUS.
Let. b1 • number of cars or buses required.
c1 = total cost per car mile in dollars for Birney Gar. c2 = total cost per car mile in dollars for Trolley Bus. h = maximum headway. 11 = one way length of route.
m :a car miles operated pe1" year 1 1. Interest on Car or Bus Investment
.06 x 6000 = ~~ 360 interest per car per year. Then 36:01:>.!. = cost per car mile. m1
2. Interest on Shop, Distribution and Transmission, and Generating and Sub-Station investments. Shop Investment $2000 per mile Distrib.& Transm. Investment 6500 It Generating & Sub-Sta- " tion Investment 4500 1T II
Total :i ~ l3000 !! l! Interest = .06 x 13,000 = ::;;780 per mile pe1"' y ear 780 1 \., Then 1 = cost per car mile m1 -6- 3. Depreciation of Shops, Sub-Stations, etc. Assumed life • 50 years Cost per year per mile 13{;000 = 0 - ~~260 260 Then 11 cost per car mile. m1 = 4. Interest on Track Investment
Cost per mile of track • ~i> 50,000
Interest m .06 x 50,000 = $3,000 per year per mile. Then 3 ,ooo 11 m cost per car mile m1 5. Track Depreciation
Assumed that track last 30 years under a 2 minute headway of 20 houi->s per day, then life in car miles • 30 x 20 x 12 trips per hour x 365 • 13,140,000 miles. Then cost per car mile per mile of track • 50,000 • $.0190 13,140,000 1 and cost per car mile for route = .0038 11
The total cost per car mile for the Birney Gar = c1 • .1334 + .0038 11 + 360b1 + 260 11 + 780 11 + 3000 11 = m1 m1 -m....1-- m1
1334 ..J. •0038 11 + 360b1 + 4040 11 m1 The total cost per car mile for the Trolley Bu:s = c2 • .1321 + 360b1 ..J. 260 11-+ 780 1 - .1321 + 360b1 + 1040 11 m1 m1 m1 1 - m1
In 01•der to find b, bl, m and m1 , o.f the f ormulae above:
Let. s • ~verage speed in miles per hour l • one way length of line h = regular headway in minutes n-h : rush hour headway in minutes. - 7 - Time f'or one round trip = 2x60 1 = 120 1 s s 'rhe buses required for rush hour service are those required for the line. Extra buses cannot be changed from route to route, because rush hours will occur at about the same time on all lines. b = 120s 1 x ri2 - 2~0111 This must be a whole number to substitute in the formula for c, as a fraction of a bus cannot be used. Since s 9 miles per hour for Bus then b 26.67 1 = = h s = 10 miles per hour for Birney Car and Trolley Bus and bl = 24 11 h
Let. h = regular headway in minutes
h - II '2' - rush hour " " n = number of hours per day of h headway n ra II It II It If 11 h 11 ~ 2 1 = one way length of route Then m 6Rm x 2 x 365 1 = 73,000 ln = ( + ~ ~ · ] h But n = 15 Therefore m = 1095000h .1 and m1 = 1095000 11 h Recapitulation of formulae developed: Let. b • number of buses required. If " cars or Trolley Buses re If Let. C2 - " " " bus " Trolley Bus. h • maximum or regular headway in minutes 1 • one way length of' bus route. 11 • " It " tt car or trolley bus route. m = number of bus miles per year. m1 = It " car or trolley bus miles per year. MOTOR BUS 1095000 1 m • h 26.67 1 , where b is a whole number. b - h .1781 .§§2£ c = + m BIRNEY CAR A.l"lD TROLLEY BUS mi s 1095000 11 h b = 24 11 where b is a whole number. 1 h 1 360b1 + 4040:· 11 c = •1334 + . 0038 1 1 . . l + m1 : .1321 3,60bl 1040 11 c2 f + mi SAMPLE UALCULATIONS 1 :a 3.5 miles 11 = 3.4 miles h a 60 minutes m 1095000 x 3.5 63875 car miles. = ------60 - = 1095000 x 3.4 60 - 62050 car miles - 9 - b 26.67 x 3.5 - 60 = 2 buses :: 24 x 3.4 2 cars or trolley buses. bl 60 - c :a .1781 + 560 x 2 $ .1956 per bus mile 63875 - _ .1 4 + .0038 x 3.4 + 360x2 + 4040x3.4 cl - 33 62050 : $ . 3793 per car mile. c 360 x 2 + 1040 x 3.4 2 = .1321 + 62050 : ~~ .2006 per bus mile. - 10 - Rour£~ -Our11ovl'llO ---/N80UNO - n - : . ~ 0 Q '.t) . ~ le) t't) \\l ...... 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UI'). ~""""/IA/ ..z ""'" ~/;:;) - 46 - V - STUDY OF CURVES 1Qn examination of the curves shows that the cost of bus operation is practically constant regardless of the number of bus miles operated. The sli~sht variation in the cost is due to the fact that when a fraction of a bus is required by for nmla, an entire bus must be used in practice. The same expla nation applies to the irregularities in the Birney Car and trolley bus curves. In practice, the equivalent of using a fraction of a car or bus would be secured by regulating the headway to eliminate hold-overs at the end of the line. The curves for the Birney Car and trolley bus are similar because of similarity in operation. With the operation o.f but a few car miles per year the cost is prohibitive because of the cost of track and trolley installation and their appur tenances. As servi oe increases, however, these large costs are more widely distributed, and because actual operation of both the Birney car and trolley bus are cheaper than the motor bus, their curves eventually cross below that of the motor bus. A study of the curves for each route will show which system of transportation is best for the service demanded. On the curves vertical lines are drawn showing the present service on each route. The curve which is lowest at this point de signates the service which is at present the most economical. VI - CONCLUSIONS - 47 - Although it is seen that the trolley bus is eventually cheaper than the motor bus, and that the point is finally reached where the Birney Car is the most economical, it must be remembered that on a given route the demands of service may never be such that a large investment for track or trolley operation is justified. Until such a point is reached, the motor bus system is the logical one to use. One of the main ad vantages of a bus is that it can be used for experimenting on a proposed route. If experience shows that such a route will not pay it can be abandoned wl thout a financial loss, since the buses can be transferred to another line. If, on the other hand, the line pays, tracks can be laid later. One cost which has not been considered in the motor bus and trolley bus, and which may in vj_ew of possible l egisla tion be a big item, is that of taxes for the use of pavement. However, should such taxes be imposed, the only effect on the curves here presented would be to raise them without chang ing their shape. These curves do not take into consideration any variations in revenue fr·om the three systems . The actual carry ing capacity of the Birney Car is about t\uenty or twenty-five percent greater than either bus, and consequently its earning capacity is greater under the same headway. The study here presented shows that buses have a very important p l ace in city transportation problems. They a re -48- yaluable in experimenting on new routes because the init:tal outlay is not so great as for the other systems, and can al- so be used for districts which need transportation service, but where such service is not great enough to warra..YJ.t the heavy investment required for tracl.: or trolly operation. They are es pecially useful in California where suburban. expansion has been unable to take care of the service required, both because of the large investment required for an initial small revenue, and because of the tj_me required for track con struct:ton.