Changing attitudes , regulations, public policy , and international treaties regarding fossil fuels are likely to lead freight railroads towards carbon -neutral technologies, yet only electri c traction matches the performance of diesel -electric locomotives. The tremendous power requirements of freight trains make efforts t o reduce greenhouse gas (GHG) emissions challenging, but the prospect of 7.2 megawatt -hour (MWh) battery -electric locomotives (BELs) offers promise, and intermittent electrification can facilitate battery charging. Train performance calculations under sim ulated real -world conditions show two 14.5 MWh combination BELs can power 8,000 -ton trains up to 230 mainline miles unassisted, with average energy consumption of 12.5 watt -hours/ton -mile. This permits discontinuous electrification of major freight lines, leaving “gaps” of up to 200 miles to reduce capital costs, especially in rugged terrain or where the power grid is sparse. Massive onboard battery arrays and intermittent access to the electrical grid for traction power and recharging provide great energ y savings through recycling energy now lost when traveling down hill or braking. A case study of a hypothetical Class I railroad found intermittent electrification with BELs more than 60% more cost -effective than contiguous electric districts, and dramatic ally reduc ed engine changes. To reduce railroad GHG emissions, governments must support technical development, show that electrification works in various North American settings, and develop institutional -financial frameworks to incentivize intermittent e lectrification with BELs, all in the context of massive environmental and capacity upgrades to electrical networks. Given proper assistance and incentives, early 21st century railroads may find discontinuous overhead -wire electrification offers great prom ise in operating terms. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 2 Keywords: Rail freight, electrification, overhead contact system, battery -electric locomotive s, charge -in-motion . INTRODUCTION As societal attitudes turn away from fossil fuel , environmental regulations are growing more stringent , carbon -limiting international treaties are being considered , and public policy is supporting moves toward non-emitting propulsion technologies, starting with well -publicized advances in the automotive sector . Until nations overhaul their electric suppli es to reduce greenhouse gas (GHG) emissions f rom power generation, there may simply be shift s in emissions from tailpipe s to power plant s. But a secular shift in public opinions is bringing creative talent to bear on the engineering challenge s of reaching carbon neutrality in transportation – including rail. Climate Change Context Human activities are estimated to have caused between 0.8°C to 1 .2°C (1.4°F to 2.2°F) of global warming above pre -industrial levels, and is likely to reach 1.5°C before 2052 ( 4). Thus, the United Nations Intergovernmental Panel on Climate Cha nge (IPCC) has called for a 40% reduction of GHG emissions by 2030 to avoid climate consequences asso ciated with average warming of greater than 1.5°C. Some industry groups describe zero -carbon rail as a “necessity” by 2050 ( 5). Diesel locomotives emit GHGs and contribute to climate change. As automobile and truck fleets are hybridized or electrified, today’s environmental arguments in favo ur of diesel -hauled freight trains as an energy -efficient form of transportation will become harder to sustain. As we transition away from a fossil -fuel based economy, some haulage needs will naturally attrit away (such as t oday’s significant tonnages of coal, crude oil, and hydraulic fracturing chemical s.) However, to continue operating in other sectors (general merchandise, intermodal, metals, farm products, and automotive), railroads must replace diesels with non -GHG -emitting propulsion technologies. Research Objectives Since the mid -1970s, the costs , benefits, and desirability of main line rail freight electrification have been debated ( 1). Credible analysts and experts have reached differing conclusions, and disagreements have even arisen among electrification advocates ( 2,3). These strongly oppos ing views often rest on very different assumptions. Thus, if diesel fuel costs $50/U .S. gallon and electricity costs $20/megawatt -hour (MWh), electrification might well cover its capital costs. Conversely, if diesel costs $2/gallon and electricity $500/M Wh, electrification will not even cover its maintenance costs. This paper makes no effort to debate the desirability of electrification. Assuming that public policy will eventually move railroads towards carbon -neutral technologies, we provide a prelimin ary quantitative analysis to demonstrate the feasibility of discontinuous or intermittent electrification in conjunction with recently -announced battery -electric locomotives (BELs) featuring 7.2 MWh of energy ( 6), assuming that those BELs are proven in ser vice and can each Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 3 be coupled to a cabless booster (or battery tender) providing a further 7.2 MWh of energy storage. This makes electrification less infrastructure -intensive and reduces maintenance costs, thus making it more affordable than continuous 20th century installations. Towards these objectives, t his work is divided into five major portions:  Review of historical background and recent technological progress towards carbon - neutrality in the railway traction arena ;  Estimation of current BEL operati ng ranges and charging times with typical freight trains, thereby deriving some basic engineering parameters and standards for an intermittent electrified national rail freight network ;  Train performance calculations to prove out that BELs have sufficient energy storage to operate over some of the most challenging terrain in the Eastern United States ;  Hypothetical case study of a Class I carrier to compare the cost-effectiveness of the intermittent electrification approach versus full electrification, inclu ding a full lifecycle cost analysis ;  Recommendations of concrete short -term pilot program actions and long er-term planning, analytical , and funding needs in terms of next steps required of industry, vendors, and governments . HISTORICAL BACKGROUND The pos t-World War II appearance of affordable, reliable, mass -produced diesel -electric locomotives transformed railroads, combining steam’s go -anywhere flexibility with the tractive force characteristics of electric locomotives. Not always remembered is that diesels in North America supplanted mainline freight electrification . Although electrification peak ed at around 1% of total U .S. railroad mileage, served crucial segments across mountains, through tunnels, and in the Northeast Corridor (7), the last electri c-powered freights ran in 1981 (Figure 1), making diesel power’s triumph all but complete. Yet r ailroads have not always been confident of the future of diesel traction . During the 1970s, several North American freight railroads, pinched by rising cost s and fuel scarcity, seriously considered electrifying their busiest lines (8 pp. 425 -428). But n o new installations ensued on common -carrier railroads, other than British Columbia Railway’s (BCR) electrification of an isolated coal -mining branch in the Can adian Rockies (Figure 2) —de-electrified in 2000 when steel industry demand for metallurgical coal fell (9,10)—and a short -lived electrification of a major freight corridor north of Mexico City. Another oil price spike in 2008 produced renewed interest in electrification (11). Then hydraulic fracturing brought about less -expensive, more plentiful oil, and railroads lost interest again . Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 4 Figure 1. Electric Conrail freight on the Northeast Corridor near the Gunpowder River, Maryland , 1980; Roger Puta photo (CC -PD0) . (https://commons.wikimedia.org/wiki/File:Conrail_E44s_ --_3_Photos_(33561299960).jpg ) Figure 2. British Columbia Railway coal branch li ne electrification, Table, B.C., 1987; Roger Puta photo (CC -PD0) . (https://commons.wikimedia.org/wiki/ File:BCRAIL_6002_at_Table,_BC_o n_September_18,_1987_(22446392399).jpg ) Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 5 Even during the 1970s with rapidly rising oil prices, electrification offered few overall cost benefits relative to diesel -electric locomotives. One major railroad held back from electrifying due to uncertainty w hether utilities could provide the amounts of power needed ( 12). Oil price spikes were brief, but financing and implementing elec trification is long and complex. New standards for locomotives (Tier 2, 3, and 4) came into force for reduc ing noxious and pa rticulate emissions from railroad operations , and thereby somewhat reduced the relative emission benefits of electrification (14), but this did not address GHG -related issues . To put matters in perspective, rail used less energy in 2018 than any other t ransportation mode: 2.0%, versus 3.1% for pipelines, and 4.3% for water modes ( 15 p. 2.12). But railroads today must consider alternatives to diesels, due to growing concerns about GHG emissions. Phasing out fossil fuels will become important for all tra nsportation modes, including railroads ( 16). Examination of how railroads can reduce their carbon footprint should include overhead -wire electrification ( 17), which can be powered from carbon -free generation sources. RECENT PROGRESS TOWARDS CARBON NEUTR ALITY The diesel era has served railroads well. Diesel provides more energy per unit mass than any other transportation fuel ( 18 p. 151). Recent sustainability efforts have produced various carbon - reduction initiatives, but few alternatives currently und er discussion are truly carbon -neutral. We now review some of the technologies cur rently on offer . “Sustainable” But Not -Quite -Zero -Carbon Experiments Florida East Coast Railway uses locomotives converted to burn liquefied natural gas (LNG), using fuel t enders (Figure 3). Although this regional railroad found satisfactory results, LNG is not carbon -neutral, particularly due to methane leakage during natural gas production ( 19) and the energy need ed to compress and chill natural gas ( 18 pp. 149 -152). Met hane is 25 times more potent as a GHG than CO 2. Since 2005, several Class I railroads have tested diesel “genset” locomotives for switching service (Figure 4). Instead of a single prime mover, genset locomotives have two or three highway -truck style eng ines that can be turned on or off individually as power is needed, improving fuel efficiency and thereby reducing overall emissions. But their unique characteristics have confined them to specialized low -power service ( 20) where their duty cycle is effici ent. Although gensets reduced particulate emissions significantly relatively to the first - generation diesel locomotives they replaced, this is not a carbon -neutral technology. A genset operating in power -hungry heavy -haul service with all engines firing most of the time can actually be less GHG -efficient overall than one with a larger prime mover. Whilst they are useful as an interim solution for switchers, they are not suitable for hauling road trains. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 6 Figure 3. Florida East Coast Locomotive 807 and Liquefied Natural Gas (LNG) Fuel Tender 302 at the Dixie Overpass, Deerfield Beach, Florida. Flickr User BBT609 photo (CC BY 2.0). (https://www.flickr.com/photos/bbt609/30873507632/ ) Figure 4. NRE 3GS21B, a popular “genset” locomotive, on Olive St., Anaheim, California, 2007; Matthew “Morven” Brown photo (CC BY -SA 3.0). (https://commons.wikimedia.org/wi ki/File:NRE_3GS21B_UPY_2733.jpg ) Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 7 In 2022, Metrolink , a California commuter rail operator, converted from fossil -fuel diesel to a renewable diesel fuel (RD99) refined entirely from modern carbon (i.e., carbon other than that contained in fossil fuels) (21). Early indications suggest that renewable diesel has comparable performance to petroleum -based diesel (22). To the extent that production of RD99 removes CO 2 from the atmosphere, overall net reductions of 65~90% of carbon emissions might be possible , but it does not entirely eliminate GHG emissions . Several heavy -haul railroads have recently ordered BELs ( 23), to be operated in conjunction with existing diesel -electric locomotives in a “hybrid” configuration, whereby energy normally lost during braki ng is recaptured and stored in onboard batteries, which are later used to power the train in conjunction with the diesels (24). Although this is a step in the right direction, it is at best an interim solution because the energy losses due to rolling and curving resistance must be replaced by diesel prime movers, which are not carbon -neutral. Elimination of GHG emissions is only complete when all energy expended in transportation can be supplied, at least theoretically, from carbon -neutral sources. Hydro gen with Fuel Cells In 2021 , a locomotive manufacturer announced a joint venture with an automotive firm to develop fuel cell technology for railroad use ( 25). Because it has only 6.4% of the energy density of diesel ( 18 p. 151), hydrogen seems unattracti ve for heavy freight operations ( 26 pp. 10-11). However, at least one major manufacturer ( 27) is fabricating a 200kW fuel cell system for use on passenger multiple units , and believes the underlying technology could be scaled up for heavy -haul application s. The majority of commercially available hydrogen today is derived from petroleum products (“blue hydrogen”); it is possible, at least in theory, to produce hydrogen from entirely non -GHG emitting sources (e.g. , solar power coupled with electrolysis of water, called “green hydrogen”). If a whole energy ecosystem is built around green hydrogen fuel cells, this would truly be a carbon -neutral technology, as the only combustion product of hydrogen is water. This process has much grid -side potential for c apturing otherwise unusable energy sources. Some of the challenges facing the hydrogen economy include the large amount of energy required to produce and compress hydrogen, relative to the energy produced when it is burnt, plus practical issues concerning large -scale storage and fueling (18). Whilst practical issues will eventually find engineering solutions, the energy input issue concerns the physical and chemical properties of hydrogen gas itself. Battery Electric Locomotives with Overhead Catenary El ectrification The rest of this paper discusses overhead catenary -wire electrification in conjunction with onboard -locomotive battery storage. To be carbon -neutral, this electricity must come from non - emitting sources. In 2022, 38% of U.S. electricity was generated from natural gas, and 22% from coal. In the European Union during 2021 , 19% of electrical power was generated from natural gas, 15% from coal , and 4% from other fossil fuels. Thus, a t present, electrification must be considered only a partiall y carbon -neutral option. However, most if not all electric power can theoretically be made carbon -free in conjunction with various form of grid-side energy storage. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 8 The b iggest challenge facing carbon -neutral electricity generation is the fact that gri d-scale energy storage solutions are needed to harvest carbon -free energy sources (e.g. wind, solar, tidal, hydro, etc.) where and when naturally occurring and available , and provide it to loads where and when required . The classic solution to this is the pump -storage generating station, but recent advances in battery technologies have made grid -scale battery storage a technically feasible proposition (if not necessarily economically viable at present , e.g. ( 28)). Progress is also being made in applying h ydrogen fuel cell technology to energy storage. In our case study, we assume that carbon -neutral power can be purchased on the wholesale electricity market where and when required, in the quantities needed —subject to the usual load planning and peak smoot hing constraints —and u se BELs solely for hauling trains where there is no catenary wire. MAKING INTERMITTENT ELECTRIFICATION WORKABLE Partial electrification by combining traditional electric operations with battery -electric locomotives (BELs) have been previously discussed (29,18 pp. 1 68). Limited battery capacity and low -cost diesel fuel were long seen as impediments. But with high oil prices, the 2021 announcement of 7.2 MWh BELs (6), and the possibility of using cabless boosters (or battery tenders) to increase energy capacity and charging bandwidth , we investigated the feasibility of electrifying parts of the network while allowing BELs to run through non -electrified “gap” sections. Such discontinuous electrification would electrify mainlines: (a) in the highest traffic density areas, (b) where electric power is inexpensive and plentiful, and (c) in strategically placed “charging islands” to reduce “gap” sections to manageable lengths. Charging islands can be located near existing power transmissio n infrastructure. Gaps would occur where the overhead catenary system (OCS) is hardest to install or maintain, or where insufficient transmission or generation capacity exist. These gaps must be long enough to produce meaningful infrastructure savings to offset the incremental costs of BELs, and they must fully recharge within islands substantially shorter than the entire route. This example aims for ~ 200-mile-long islands, with a 50% mark -to-space ratio goal (i.e., on /off ratio or duty cycle) between electrified sections and gaps. This would require BELs with a 200 -mile range in normal freight service. Figure 5 illustrates conceptually the difference between current diesel operation and BELs . Figure 6 shows an artist’s conception of what BELs operat ing in charging mode might look like in the Midwest , where electrical energy and power infrastructure might be comparatively less costly. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 9 1,000 miles Lineart by RailToonBronyFan3751 at DeviantArt (CC-BY NC 3.0) 5,000 gals 190 MWh2,500 gals 95 MWh3,750 gals 142.5 MWh1,250 gals 47.5 MWhRefuel 14.5 MWh 200-mile Electrified Segment200-mile Electrified Segment 4 hours charging @ 3.7 MW + hauling @ 3.3 MW4 hours @ 7.0 MW 4 hours hauling @ 3.3 MW (4,400 hp) Figure 5. Concept of Intermittent Electrification with 200 -Mile Long Charging Islands and 50% Mark -to-Space Ra tio. Figure 6. Chicago & North Western B attery Electric Locomotives Charging through the Prairies; Artist’s C onception by John G. Allen. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 10 Illustrative Example Compared to European Approaches At this point it is important to differentiate this work from a previous European concept termed “intermittent electrification” with very short live -wire segments and gaps ( 30), on the order of several hundred meters to several kilometers (sometimes termed “overhead line islands”) , applied to reducing GHG emis sions with dual -mode diesel locomotives ( 31). This concept was found to be unworkable for mainline electrification due to feeder wire cost and substation -related issues ( 32), although Deutsche Bahn may be close to implementing such a concept for rural passenger rail in Schleswig -Holstein ( 33), where the lower power requirements have more in common with buses . Our concept of “intermittent electrification” calls for long segments of electrified railway featuring multiple supply substations , from tens o f miles up to several hundred miles , separated by long gaps of up to two hundred miles that could be covered by fully -charged battery electrics. Within these long segments, there may be short neutral sections of up to a mile in length, where clearance or other constraints make catenary electrification extremely expensive. Figure 7 shows a hypothetical illustrative example of what an intermittent electrification scheme might look like for the Alphabet Route ( a coalition of railroads connecting the Midwest United States with the Northeast, as a freight alternate to the major syst ems (34)) had it continued to operate today . (This version adds the Rock Island from the Quad Cities (Davenport and Bettendorf, Iowa, and Rock Island and Moline, Illinois ) to Chica go, a branch from Indianapolis, and eliminate the New England portion which would otherwise use today’s Northeast Corridor .) Quad CitiesChicago Toledo St. LouisPittsburgh BaltimorePhiladelphiaNorth JerseyI-84 IMX IndianapolisPWV segment with 13 tunnels (not electrified)Norris Tunnel Sand Patch East Slope with 3 tunnels, otherwise electrified for gradientWM segment with 5 tunnels (not electrified)Non-electrified segment Electrified segment (white gaps indicate short neutral sections)“Alphabet Route” Electrification Scheme (Conceptual) 0 50 100 150 200Approximate scale in miles Figure 7. A conceptual illustration of what an intermittent electrification scheme for the consortium known as “Alphabet Rout e” (with minor additions and subtractions) could look like. The remainder of this paper presents calculations to validate the range capabilities of current BELs , economic analyses of representative case studies, and next steps required to bring this conc ept closer to reality. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 11 Estimating BEL Range via Comparison to Diesel -Electrics Typical ly, North American freight diesel s carry 5,000 gallons of fuel and run ~1,000 miles between refueling. Diesel’s energy density is ~36 megajoules (MJ) per liter, or 37.9 kilowatt - hours (kWh) per U.S. gallon. A full tank therefore contains about 190 megawatt -hours (MWh) of energy. However, diesels are on average about 40% efficient (comparable with typical thermal generating station s), leaving only ~75.7 MWh available at the drawbar. Energy requirement s in “average ” freight service are therefore around 75.7 kWh per mile. How many miles can BELs travel with these energy requirements? The 7.2 MWh are delivered to the railhead with around 95% efficiency, leaving 6.8 MWh f or traction. However, BELs store some energy now lost through rheostatic braking on diesel -electrics. If 50% of this energy is recaptured (consistent with 30% claimed fuel savings when operat ed in tandem with diesel - electrics), the 6.8 MWh “virgin” energ y plus 3.4 MWh of “recycled” energy produces total output s of 10.3 MWh before batteries are exhausted, or a 135 -mile range at 75.7 kWh/mile. Can this be extended to a more useful 200+ miles? Attaching a cabless booster containing a further 7.2 MWh would extend the estimated range to 270 miles. Even with the additional weight, this is still comfortably above the target 200 -mile range. The 14.5 MWh available from a two -segment locomotive (23) is an immense amount of energy, and with intermittent electrifi cation, gives diesels serious competition. Although these range estimates remain to be proven, a study from a mainline pilot program in California came to broadly consistent conclusions (35), predict ing that in terrain substantially hillier than our assum ptions, 7,500 -ton trains with 14 -MWh batteries would have a 150 -mile range, implying energy consumption of 93.3 kWh/mile. Estimating Required Lengths of Charging Islands North American freight trains average about 20 -25 mph. However, this range conceals great variation because of network fluidity and other operating issues. If congestion is low, freights can average 40 mph, taking about five hours to travel 200 miles. Presently, BELs are advertised as achieving full charge after four hours on high -volta ge catenary (6). This suggests in most cases, BELs can charge fully at service speeds through 200 -mile-long charging islands. Battery Technology Assumptions Current grid -scale batteries, and batteries for electric cars and aviation applications are typ ically based on Li -Ion or Ni-Metal -Hydride battery chemistry —similar to batteries used in laptop computers —although there is no shortage of other contenders (e.g. , (36,37)). Some creative solutions have been proposed for railroad applications ( 38), indee d a hydrogen fuel cell stack could itself be considered a form of battery. Current grid-scale batteries typically have a C/4 charging rate (39). We therefore assumed that whatever the battery chemistry, batteries can be designed to meet those charging ra te, capacity, weight, and volume constraints. Certainly, other studies (35) have found these generic specifications are feasible within the dimensions and weight limits of railway vehicles. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 12 Designing Catenary Gaps for Infrastructure Cost Savings Even i n otherwise -electrified zones, railroads can design short gaps for low -clearance situat ions such as draw bridge s, structures , and tunnels, to keep infrastructure costs down. This would be a different, more flexible way of electrifying , as trains could run in battery mode through these obstructions . Figures 8 and 9 show artist’s conception s of situations where this type of money - saving design s might be applicable . Provided that locomotives can leave each 200 -mile-long charging islands fully recharged, the charging island themselves can be discontiguous. (This situation already exists on the Northeast Corridor in southwestern Connecticut, where there is a short gap in the wires when crossing the Cob movable bridge over the Mianus River.) These “short” gaps , of perhaps up to a mile in length , can be provided where clearances or geographic features render electrification extremely expensive. It is even possible for the head - end of the train to be operating in battery mode over a long neutral section, whilst a distributed power ( DP) unit further back in the train continues to power in electric mode , because that unit is still on the live wire. Figure 8. New York Central on the Restricted -Clearance Cuyahoga River Drawbridge, Cleveland, Ohio; Artist’s Conception by John G. Allen . Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 13 Figure 9. Chessie System Fruit Juice Unit Train at Mount Royal Station, Baltimore, Maryland; Artist’s Conception by John G. Allen . Estimating BEL Range by Train Performance Simulation This “average” estimation approach b y comparison with diesels leaves some uncertainty that BELs would be suitable for certain duty cycles over specific types of terrain. To show that BELs can handle most traffic types over all types of terrain, we performed Train Performance Calculations (TPC, Table 1) using industry standard formula s (40,41). These estimates, although back -of-the-envelope by nature, show that energy demand per mile varies dramatically by terrain. But it typically averages out about 100 kWh/mile for an 8,000 -ton train, con sistent with estimates from other calculations above. Most energy is consumed by rolling resistance. Because what goes up must come down, terrain constrains operations only in that BELs must not run out of energy before cresting the summit (Figure 10(a-b)). Early 20th century railroad electrification schemes focused on providing consistent power in mountainous terrain to reduce or eliminate pusher locomotive requirements (and steam locomotive firemen’s workloads). In a BEL world, intermittent electrifica tions should be planned on a network -wide basis while ensuring each locomotive has sufficient energy reserves to crest the summit. This might concentrate electric supply needs in foothill areas, where electrification is cheaper to install than building overhead line equipment through rugged terrain (42). Intermittent Electrification with Battery Locomotives and the Lu and Allen Post-Diesel Future of North A merican Freight Railroads 14 Energy Requirement in Megajoules (MJ) Megawatt -hours (MWh) Line Segment (A) MP Start (B) MP End (C) Dist. (Miles) (D) Elev. Gain (ft) (E) Elev. Loss (ft) (F) Wt. Avg. Curve Deg. (G) Lift (H) Descend (J) Rolling Resist. (K) Curve Resist. (L) Accel. (M) Decel. (N) Starting (P) MWh Demand (Q) MWh Recov - erable (R) MWh Total (S) MWh /Mile (1) 373.0 394.5 21.5 1,580 0 1.50 34,287 0 2,331 1,469 0 0 0 10.7 -0.2 10.5 0.488 (2) 373.0 394.5 21.5 1,580 0 1.50 34,287 0 2,331 1,469 287 0 2 10.8 -0.2 10.6 0.493 (3) 394.5 454.0 59.5 0 1,425 1.50 0 -30,923 10,217 4,065 860 0 0 4.1 -8.6 -3.8 -0.064 (4) 373.0 454.0 81.0 1,580 1,425 1.50 34,287 -30,923 13,910 5,534 860 0 0 14.8 -8.8 6.7 0.082 (5) 454.0 373.0 81.0 1,425 1,580 1.50 30,923 -34,287 12,365 5,534 591 0 0 13.3 -9.5 9.8 0.121 (6) 55.6 84.0 28.4 169 95 0.87 3,667 -2,062 4,877 1,124 1,021 0 0 2.7 -0.6 2.4 0.085 (7) 155.4 204.2 48.8 533 530 0.33 11,566 -11,501 13,159 734 1,434 0 0 7.1 -3.2 4.4 0.090 (8) 0.0 128.0 128.0 580 610 0.05 12,586 -13,237 31,346 292 9,783 -8,654 0 15.0 -6.1 9.9 0.077 (9) 454.0 373.0 81.0 1,425 1,580 1.50 61,846 -68,574 21,990 11,069 717 0 0 26.7 -19.0 19.7 0.243 Line Segments Column Explanation (1) Sand Patch Grade, Westb ound on East Slope (ES) (2) Sand Patch Grade, WB on ES w/ Restart Mid -Grade (3) Sand Patch Grade, Westbound on West Slope (4) Sand Patch Grade, Westbound (Both Slopes) (5) Sand Patch Grade, Eastbound (Both Slopes) (6) Akron Mainline, New Castle Jct. PA to Niles OH (7) Akron Mainline, Sterling OH to Willard OH (8) Chicago East Subdivision, Willard OH to Garrett IN (9) Sand Patch Grade, Eastbound , 16,000 -ton train Assumptions:  8,000 ton train with 80 cars and 25 ton axle load.  Average speed of 20 mph ascendi ng/40 mph descending Sand Patch Grade EB, and 20/35 mph Westbound; 40 mph on Segment (6), and 60 mph on Segments (7) and (8) ; 30 mph on Segment (9) . Curvature data is from a Chessie System Track Chart of 03-22-1985. Some curvature values were estimated from Google Maps for track segments not covered by the track chart. Speed restriction data are from CSX System Employee Timetables (2005). (D),(E) (F) (G) (H) (J) (K) (L) (M) (N) (P) (Q) (R) (S) Total gain/loss in elevation within the line segment, in feet. Weighted average curvature in degrees. This is the sum of (degrees of curvature curve length) for all curves, divided by the total line segment mileage. Useful in calculating curving resistance. Energy expended in lifting the train through the elevation change. P.E. = mgh (g = 9.81 m/s/s) Energy released in allowing the train to descend through the elevation loss. Energy expended in overcoming rolling resistance. Modified Davis Formula (1970), see ( 41). The output is in lbf (Pound -Force) per U.S. ton, converted to energy using W.D. = force  distance. Energy to overcome curving resistance. 0.8 lbf per trailing ton per degree of curvature ( 40). Energy expended in accelerating train to desired speed, including for observance of any speed restrictions. K.E. = ½ mv², energy required in accelerating is the difference in K.E. between current speed and target speed. Segment (7) included seven 40 mph permanent speed restrictions (PSR) and one 50 mph PSR with a general line speed of 60 mph. Segment (3) and (4) accounts for acceleration at the summit from 20 mph to 40 mph. Energy generat ed in braking train to desired speed, assuming 100% regenerative braking. Energy expended in starting the train from a standing stop. 5 lbf per training ton, moved one foot. Total energy required to move the train through the line segment. Theoretical max imum energy potentially recoverable from regenerative braking. Practical total net energy required to move train through the line segment after accounting for normal 95% regenerative braking efficiency, and maximum battery charging rate (linear) of C/4 ( 3.6MW). Average energy consumption in MWh per mile travelled. Table 1. Train Performance Computations for Selected Line Segments between Baltimore and Chicago. Intermittent Electrification with Battery Locomotives and the Lu and Allen Post-Diesel Future of North A merican Freight Railroads 15 (a) Projected Battery Charge Level Westbound Unelectrified from Cumberland, Md. to Connel lsville, Penn. (Initial Charge = 100%) (b) Projected Battery Charge Level Westbound Unelectrified from Willard, O. to Garrett, Ind. (Initial Charge = 90%) 02468101214 368 378 388 398 408 418 428 438 448 458Charge Remaining (MWh) Mile PostCumberland Subdivision Theoretical Maximum (95%) Charge Rate Limited (C/4) No Regen (Worst Case) 02468101214 724 734 744 754 764 774 784 794 804 814 824 834 844Charge Remaining (MWh) Mile PostWillard & Garrett Subdivisions Theoretical Maximum (95%) Charge Rate Limited (C/4) No Regen (Worst Case) (c) Grade Profile for Main Line from Chicago, Illinois to Baltimore, Maryland via Sand Patch, Pennsylvania 02505007501000125015001750200022502500 -974 -954 -934 -914 -894 -874 -854 -834 -814 -794 -774 -754 -734 -714 -694 -674 -654 -634 -614 -594 -574 -554 -534 -514 -494 -474 -454 -434 -414 -394 -374 -354 -334 -314 -294 -274 -254 -234 -214 -194Garrett, Ind. Willard, Ohio New Castle, Penn. Pittsburgh, Penn. Connellsville, Penn. Cumberland, Md. Frederick, Md. Baltimore, Md.Sand Patch SummitElevation /ft. Milepost Figure 10. Train Performance Computation Results for 14.5 -MWh BEL -Booster Combinations Hauling 8,000 Trailing Tons over Selected Line Segments Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 16 Sand Patch Grade in southwestern Pennsylva nia’s Laurel Highlands (Figure 10(c) and 11) is one of the longest and highest such east of the Mississippi River. Its energy requirement is only 10.7 MWh, well within the capability of a 14.5 MWh locomotive -booster combination (Table 1). However, descending very steep grades (like Sand Patch eastbound) g enerates energy faster than onboard batteries can recharge at 3.6 MW, which leads to incomplete energy recapture, reducing the travel range for the remainder of that move. Figure 11. Eastbound Chessie System Freight Train About to Enter Former Tunnel on Sand Patch Grade, 1987; Bruce Fingerhood Photo (CC -BY 2.0) . (https://commons.wikimedia.org/wiki/File:West_portal_sand_patch.jpg ) To the extent that railroads with ste ep downhill grades generate more power than onboard batteries can absorb, they can be used as sources of electric power generation. As with hydroelectric generating stations, they produce electricity through gravity. Where sufficient train densities exis t, such locations could be connected to the grid via catenary wires, to allow energy to be captured and utilized elsewhere. Significantly, and contrary to conventional wisdom, this result indicates that gently undulating terrain in much of the Eastern Uni ted States , the Midwest, or the Great Plains would have Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 17 virtually no impact on the operating range of BELs. However, in rugged terrain where average gradients exceed about 0.4% (1-in-250), the energy generated by descending train s could exceed battery re -charging bandwidth, resulting in lost energy through rheostatic braking and therefore in reduced BEL range. This issue can be addressed at an operational level by adding extra BELs to the consist within that “mountain district”, or by providing additional segments of electric catenary where needed , either to provide supplement ary power uphill or to absorb excess power downhill . Motive Power Assignment Assuming 200 -mile gaps between 200 -mile-long electric districts, motive power desks would need to develop locomotive assignment rules, much as fleet offices keep track of locomotive mileages , diesel fuel levels , and minimum horsepower -per-ton today. Based on a 12.5 watt -hour (Wh)/ton -mile consumption rate, plus a 25% “protect” factor to account for unschedul ed stops, and 5% efficiency losses, each 2,000 tons would require just under 7.2 MWh of battery capacity (with a 3.4 MW nominal output rating) . At virtually 2. 3 horsepower -per-ton, a train thus assigned should be able to move through any reasonable terrai n. Typical 8,000 -ton trains might currently operate with two 4,400 hp units, each carrying 5,000 gallons of diesel fuel. This train would need four 7.2 MWh units (or two 14.5 MWh, dual- segment BELs). The 200 -mile mark -to-space (i.e., on -off) ratio for i ntermittent electrification is thus within reach, assuming typical power desk practices, and that the 14.5 -MWh combination is proven in service. Railroads carrying very heavy commodities such as aggregates, ore, lumber, or paper, or with specific operatin g philosophies preferring very lo ng trains, require operation of land barges weighing anywhere from 16 ,000-tons to 24,000 -tons. Movement bureaux would obviously need to assign additional power to these specific trains, potentially requiring up to eight 7. 2 MWh units to make the 200 -mile range at 16,000 -tons. Railroads may need to adjust their operating strategies, discussed below. Alternatively, the locomotive range requirement could be reduced by e.g. electrifying heavy -haul segments with 1 00-mile gap s between 100-mile-long electric districts, which would approximately hal ve the motive power energy storage requirements (thus using four 7.2 MWh units to make the 1 00-mile range at 16,000 -tons, which at 1. 1 hp/ton would likely still have sufficient power to move the train over the road). However, this design would require the average speed over the segment to be reduced to about 25 mph, to allow the locomotives to be fully charged within 100 -mile-long electric districts. On a heavy -haul district, this lo wer average velocity may not represent an insurmountable problem —and may in fact be desirable. When EMD FT diesels were built between 1939 and 1945, they had 1,350 hp of installed power. Then, the most powerful steam locomotives developed 4,000 -6,000 hp, thus diesel consists of four units in A -B-B-A configuration (Figure 12) were often necessary to replace a single steam locomotive. Multiple units were necessary for power reasons in the steam -diesel transition and will be needed for range reasons in dies el-BEL substitution. Higher future cell energy densities will doubtless improve this. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 18 Figure 12. Great Northern Railway EMD FT Locomotives, 1943; Courtesy of the Minneapolis Tribune. (https://commons.wikimedia.org/wiki/File:Great_Northern_EMD_FT_locomotive_1943.jpg ) Regardless of electrification infrastructure design choices, new engine desk assignment rules would be needed for dispatching BELs, tak ing tonnage, physical characteristics, speeds (which affect rolling resistance and regenerative recharge rates), energy storage capacity, haulage (power) capability, and initial charge level into account —replacing the horsepower -per-ton heuristics of yeste ryear. This could make the power desk task that much more complex and software decision -support tools may need to be developed. Locomotive Design Assumptions Implied in these calculations are certain design assumptions about the BELs. The available information suggests that 7.2 MWh can be carried on two standard three -axle trucks, but based on current battery technology, 14.5 MWh would require a two -segment design for space or weight reasons, or both. This assumption suggests various form factors may be possible to achieve the desired 200 -mile range, as shown in Table 2. The precise form factor that balances operating convenience and cost is a matter of electrical and mechanical engineering and is outside the scope of this paper. The detailed design of locomotives is unimportant to this research; the point is that 14.5 MWh is sufficient to power an 8,000 -ton train for more than 200 miles (and a 16,000 -ton train for more than 100 miles) under typical operating conditions. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 19 Name Description Frames Cabs Panto - graphs Trans - formers Trucks Traction Motors Articulated Single locomotive with two articulated parts 2 1 1 1 3 3-axles 9 Two-Segment One locomotive with a cabless booster, similar to EMD FT -A and FT -B 2 1 2 2 4 3-axles 12 Two Separate Locomotive s Two 7.2 MWh locomotives can be utilized separately 2 2 2 2 4 3-axles 12 Extra Long Frame Single locomotive, like EMD DDA40X 1 1 1 1 2 4-axles 8 Permanently Coupled Two locomotives permanently joined 2 1 1 1 4 3-axles 12 Double -Ended Single articula ted locomotive with two cabs, like an articulated version of EMD ML2 2 2 1 1 3 3-axles 9 Table 2. Possible Form Factors for 14.5 MWh Freight Service BELs . Estimating Required Substation Ratings Based on parameters sketched out for the 200 -mile chargi ng islands, we might expect that where the traffic is moderately busy, on a multi -track mainline there might be eight trains per hour. Assuming industry standard 25kV 60Hz alternating current ( AC) electrification, each supply substation might cover about ~40 route -miles of territory, so five supply substations would be needed per charging island. At eight trains per hour, each train taking an hour to traverse the territory at 40 mp h, all eight might be drawing power simultaneously within the segment. Assuming that each train carries on average 12,000 tons, or is equipped with six 7.2 MWh units that charge at C/4 rates ( i.e., taking four hours to charge to 100% capacity), the total power draw due to battery charging alone is 10.8 MW per train, or 86 MW tot al. If we assume two of these eight trains are actively accelerating, and another four are maintaining speed at half power, the power draw due to real -time energy use is another 40 MW. This potentially calls for a 12 5 MW substation rating, which is actua lly only slightly larger than supply substations (Figure 14) for a typical heavy duty 25 kV passenger railway electrification, which are in the 50 MW to 80 MW range. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 20 Figure 14. Passenger Railway Supply Substation on the Northeast Corridor. Although BEL technology scales well, in that a heavier train can always be hauled by adding extra locomotives in the consist which results in negligible changes to the locomotives ’ (thus the train’s) total mileage range between need to recharge, supply substat ions do not necessarily scale well, as it becomes very expensive to provide for that peak power load. For that reason, when railroads are transitioning to electrified operations (with or without BEL s), it may be necessary to make operating plan changes an d/or invest in energy management systems as to spread out or limit the load that is drawn from the power grid at any given moment. Diesel electrics get around this problem by essentially being mobile power plants that are operated in parallel as needed. Based on typical carrying capacities of high -voltage distribution circuits, about two -thirds of the capacity of a three -phase 132 kV circuit would be needed to fully supply one such 12 5 MW substation. With five ±25kV supply substations within a 200-mile-long charging island, it should be understood that the substations would most likely need to be connected to the supergrid operating at between 275 kV and 500 kV, requiring substantial coordinated planning with electric utilities, and possibly dedicated gen eration capacity. This is already the current practice for substations on the electrified high -speed passenger rail network in Europe ( 26 p. 27), due to the sheer magnitude of unbalanced load represented by power -hungry high speed trainsets. Another alte rnative to planning for the exceptional power load would be to limit the average number of trains or average tonnage that is permissible over that segment. The p ower requirements of charging multiple units in parallel will have important implications for substation ratings and cost. Although it’s possible to install smaller supply substations at more Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 21 frequent intervals, adequate transmission and generation capacity would still need to be provided for. This would have significant implications on the optim al train lengths to be carried on an electrified network compared to a diesel one , possibly requiring shorter, more frequent freight trains . The optimal design choices balancing all those variables would not be knowable without working out the specifics f or one particular installation. Current and Voltage Choice Electrifying railroads on a continent -wide scale involves some issues that may not arise with smaller projects. Given the different geographies where electrification would occur, no single voltag e will suit all needs. 25kV is the industry default standard, but 50kV may be more suitable for rural areas with sparse supply. Locomotives needing to operate on the N ortheast Corridor will need 11 kV 25Hz capability. Different transmission and feeder ar chitectures may also be required, with consequences in resiliency, signal interference, and maximum substation spacing, as discussed in prior studies (43 pp. 6.1 -6.5). The 7.2 MWh BEL, if allowed to accelerate whilst charging, can draw up to 4.5 MW of pow er, which lower electrification voltages would have difficulty supplying . At 750V DC , this translates to 6,000 Amperes (A) , or 1,200~1,500A per shoe, which is near the upper limit of what is reasonable. Assuming that railroads would occasional ly need to operate 1 6,000-ton trains, eight such BELs would be required to achieve the 200 -mile range, and the total power draw would be 36 MW. 750V or 1.5 kV DC substations are typically limited to about 10~15 MW, which means medium -voltage DC electrification is no t a realistic proposition for modern BEL -enabled freight electrificatio n. Even if the substations could be uprated, the sheer magnitude of negative return current would be prohibitive. Although BELs should be workable down to 11 kV AC, the lower voltages found on DC systems require currents that are too high . Higher Voltage for Heavy -Haul or Rural Applications At ±25kV AC electrification, this translates to 180A at the pantograph (and half of that in the rails for traction return), which is quite reasona ble. With eight units online simultaneously, the potential traction return current is 720A, which is still within the acceptable range. However, some railroads that have consider ed electrification found 25kV AC restrictive for their requirements. When p ower of 10,000hp and upwards is necessary, even with 25kV , substations might have to be located comparatively close together, which is neither desirable nor even possible in some locales. 50kV offers much greater flexibility , providing there are not too m any low bridges (44 p. 202). If heavy haul operations are anticipated with the routine use of six - or eight -BEL consists, then ±50kV AC electrification could be considered, to reduce the current required (and secondarily to allow potentially higher substa tion spacing, although at high power consumption it would not be electrically efficient to push substation spacing close to its practical limits.) Illinois Central Gulf considered 50kV between Chicago and New Orleans. With their power requirements, the s ubstations w ould be located at 30 -40 mile intervals . Over much of the route the electric utilities have adjacent power lines, thereby eliminating the need for feeders to be erected specifically for the railway’s use ( 45 p. 199). Similarly, British Columb ia Railway chose 50kV in the Canadian Rockies for electrical efficiency (9 p. 14) , allowing it to power the entire installation with just one substation. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 22 Summary of Design Trade -Offs Table 3 summarizes the design trade -offs that should be considered when planning an intermittent electrified railway n etwork with BELs, along with realistic working assumptions chosen by the authors for the case study in the next section. Note that some of these variables are related, e.g. choices in maximum train size would affect required BELs per train, substation ratings, and substation spacing. Variable Range s to Consider Default for This Study Average Train Size 8,000 to 24,000 tons 8,000 tons Electric District Size 50 to 200 miles 200 miles Catenary Voltage 11 kV to 50 kV AC 25 kV AC Supply Substation Rating 50 to 125 MW 125 MW Supply Substation Spacing 20 to 40 miles 40 miles BELs per Train 2 to 12 7.2 MWh BELs 4 7.2 MWh BELs Average Freight Train Speed 20 mph to 50 mph 40 mph Maximum Average Gradient 0.2% to 1.0% 0.4% (1 -in-250) Mark -to-Space Ratio 66.7% to 50% 50% Utility Connection Voltage 132 kV to 500 kV 400 kV Train Den sity 10 ~ 100 trains per day ~ 25 trains per day max. Table 3 . Trade -Offs to Consider When Designing Intermittent Electrification Systems . NETWORK PERFORMANCE ANALYSIS We used a simple project evaluation model to examine a hypothetical rail freight network, including practical issues facing Class One railroads, such as interline traffic, varying terrain, etc. Although recent literature argues that converting diesels to battery locomotives without electrification would save money based on off -peak re charging on the wholesale electricity spot market ( 35), industry reception has been unenthusiastic ( 46). When externality costs are removed, even that study showed $5.85 million in diesel locomotive costs versus $6.47 million for BELs. Yet others argue t hat the underlying business cases may be sound in certain corridors, warranting further investigation ( 47). Because of sunk investments in diesel locomotives, shops, and workforce skills, change will occur incrementally. We accommodate this incremental approach and show how intermittent electrification makes good use of BELs’ practical advantages. Hypothetical Electrification Case Study The case study network (Figure 15(a)) is a hypothetical east -west Class I railroad with 2,195 route miles, whose pred ominant traffic patterns form an approximate “X”, but also with significant north -south flows that do not pass through the middle of the “X”. This railroad has 60 daily train starts between important origins and destinations (Table 4(a)), with up to four pairs of daily departures in the busiest corridors, and one daily departure in quieter service lanes. Two Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 23 strategies are examined: intermittent (discontinuous) electrification (Figure 15(b)) and contiguous electrification (Figure 15(c)). Both strategies cost 50% less than full electrification when completely built out. We do not consider a charging -pad scenario where locomotives are charged while stabled or serviced at intermediate terminals, as there are practical difficulties with that set up ( 29) and at current maximum practical charging rates it does not achieve good utilization of movable assets. Trains of 8,000 tons are assumed. These can be reliably handled by two diesels, or two 14.5 MWh combo -BELs. This analysis can be readily scaled up to 1 6,000 -ton trains using four combo -BELs. No attempts were made to model this railroad for specific commodities. Local pick-ups and deliveries were not considered. On the engineering side, 2,195 route -miles were divided into 15 districts, and each was ass igned cost factors based on terrain and proximity to large metropolitan areas (Table 4(b)). Electrification unit cost assumptions are broadly consistent with currently available industry data (48,49). Table 4(c) shows assumptions about locomotive price and availability. Maintenance -of-way and train crew costing follows established zero -based methodology ( 50) with assumptions about infrastructure (substation counts , interlockings, etc.), labo ur rates, gang productivity, and crewing methods consistent wit h typical Class I practice. Note that electrification has an effect on Signal, Comm unication s, and Track & Structures Maintenance of Way costs because additional infrastructure is needed to support electrification, as well as the increased complexity in c oordinating work due to the need for power isolations (see e.g. ( 51)), impedance bond disconnections, and working within restricted overhead clearances on tasks such as rail replacement and track production (see e.g. ( 52)). System costs were allocated pro portionately. We were unable to estimate locomotive maintenance costs, as BEL maintenance costs are necessarily speculative. Batteries will eventually decline in usable capacity and must be replaced. BEL units are likely to need five - yearly battery over hauls, much as diesels need prime mover rehabilitation (although on somewhat longer intervals). Significant unknown s include the costs and environmental impacts of battery fabrication and disposal , and the consequences of mining the necessary semi -preciou s metals. We outlined multiple stages for project implementation for both intermittent electrification (Figure 15(b)) and contiguous electrification (Figure 1 5(c)). For each stage, we estimated performance metrics, including electrically powered train -miles, daily engine changes required, investment cost -effectiveness, and transportation, maintenance, and fuel cost impacts. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 24 (a) Network Map with Nodes and Mileages C BA DE G F HJ L K250 38565 100100 30 40 225450175375 (b) Four Phases of Intermittent Electrification C BA DE G F HJ L K21 2 334 (c) Three Phases of Contiguous E lectrification C BA DE G F HJ L K31 22 Figure 15. Maps for Hypothetical North American Class I Electrification Case Study. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 25 (a) Traffic Dept. Assumptions (Daily Trains ) (c) Mechanical Department Assumptions Origin A B C D E H K L Ttl Destination A 0 2 1 0 1 0 1 5 B 0 4 2 0 0 2 4 12 C 2 4 2 2 2 0 0 12 D 1 2 2 1 1 2 1 10 E 0 0 2 1 0 0 1 4 H 1 0 2 1 0 0 1 5 K 0 2 0 2 0 0 0 4 L 1 4 0 1 1 1 0 8 Ttl 5 12 12 10 4 5 4 8 Locomotive Type Battery Electric Straight Electric Diesel Electric Capab ility detail Catenary operation and recharging capability, 14.5 MWh including integral battery tender Medium horsepower freight type unit, 5,500 peak hp, 75 mph speed limit High -horsepower AC traction unit, 4,400 hp Purchase cost (per unit) $10 million $6 million $5 million Shop margin for maintenance 20% 10% 15% (b) Engineering Department Assumptions Equip ment Counts Infrast ructure Costs ($ mil lions) (A) Line (B) District (C) Character (D) Route Miles (E) # CPs (F) # // Subs (G) # Supply Subs (H) # Radio Bases (J) $ Cat. (K) $ Elec. CP (L) $ // Stn (M) $ Supply (N) $ Total CJ CJ-1 Metropolitan 55 6 6 1 6 $550 $60 $150 $75 $835 CJ CJ-2 Rural 135 7 14 3 14 $540 $28 $140 $90 $798 CJ CJFG -1 Rural 60 3 6 2 6 $240 $12 $60 $60 $372 JF CJFG -2 Industrial 30 3 3 1 3 $180 $18 $45 $45 $288 FG CJFG -3 Industrial 40 4 4 1 4 $240 $24 $60 $45 $369 DJ DJ-1 Industrial 100 5 10 3 10 $600 $30 $150 $135 $915 LJ LJ-1 Rural 175 9 12 3 18 $700 $36 $120 $90 $946 LJ LJ-2 Rural** 150 8 10 3 15 $750 $40 $125 $113 $1,028 LJ LKJ-1 Rural 60 3 4 1 6 $240 $12 $40 $30 $322 LJ LKJ-2 Rural 65 4 5 1 7 $260 $16 $50 $30 $356 KJ LKJ-3 Rural 100 4 5 2 10 $400 $56 $50 $60 $566 GE GE-1 Lakeside 175 6 18 4 18 $875 $30 $225 $150 $1,280 EA EA-1 Industrial 200 10 20 5 20 $1,200 $60 $300 $225 $1,785 EA EA-2 Industrial 175 6 12 3 18 $1,050 $36 $180 $135 $1,401 GB GB-1 Rural 170 9 17 4 17 $680 $36 $170 $120 $1,006 GB GB-2 Mountainous 150 8 15 4 15 $1,200 $64 $300 $240 $1,804 GB GB-3 Exurban 90 5 9 2 9 $540 $30 $135 $90 $795 GB GB-4 Metropolitan 40 4 4 1 4 $400 $40 $100 $75 $615 FH FH-1 Rural 225 8 12 4 23 $900 $120 $120 $120 $1,260 Total 19 2,195 112 186 48 223 $11,545 $748 $2,520 $1,928 $16,741 Notes: ** This District contains a short Metropolitan segment. Column (E) = Count of Interlockings (CPs); (F) = Count of Paralleling Substations; (G) Count of Supply Substations; (H) Count of Radio Bases; (J) Electric catenary construction costs; (K) Special catenary work at Interlockings. Costs are factored based on Column (C ), includes all Civil/Right -of-Way work, and excludes land acquisition/cost of leasing staging areas. Columns (D) through (H) used in estimation of Maintenance of Way costs. Other Key Assumptions: Electrification with ±25kV 60Hz architecture. Diesel price = $6.00 per gallon; Electricity price = $110 per MWh. Fringe & benefits overhead = 80%; Pay Rates: Linemen, Signalmen, Welder $35/hr; Trackman $25/hr; Dispatcher/Supervisor $40/hr; Train & Engine Crews = $375 daily; Crew District Size = 300 miles; C rew Overhead Ratio (Absence/Vacation/Training) = 30%; Crew Size = 2; Discount Rate = 5%. All costs are strategic estimates, actual costs will depend on designs, labor agreements, and other factors. Table 4. Assumptions for Hypothetical North American Cl ass I Electrification Case Study Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 26 Findings This case study clearly shows that substantial investment is needed for any rail network electrification. It is not clear at all where the financial savings would come from to repay that investment, as electrifi ed railroads are more expensive to operate and maintain than non - electrified ones (Figure 16(a)), due to their increased fixed plant, higher complexity, and interaction between different maintenance groups. Under current conditions, the anticipated ener gy cost savings do not offset the investment and maintenance costs of electrification in any scenario. Table 5 shows the shortfall. However, obviously these costs could easily change based on relative prices of diesel versus electric power and are sensit ive to electrification cost estimates. So long as less than 100% of the rail network is electrified, any electrification imposes an efficiency penalty, as locomotive changes tend to reduce fleet utilization, require larger fleets, and increase service di sruption risks (Figure 1 6(b)). All these reasons explain the industry’s current reluctance to embrace electrification. However, if public policy moves railroads into a post -diesel world, the intermittent electrification approach phases out diesels quicke r and at a lower cost (Figure 1 6(c)). This produces more train-miles under electric traction and does so sooner than a contiguous “electric district” approach. It has the additional advantage of substantially reducing operating complexity by reducing eng ine change s. The fleet impacts have a more complex, nonlinear relationship with electrification levels and strategies, as do diesel -train-miles operated “under the wires”. But, if we examine the investment cost effectiveness measure of dollar investment per annual zero -emission train mile, the intermittent electrification strategy outperforms a contiguous electric district in all project stages (Figure 1 6(d)), being usually over 60% more cost effective. Even a contiguous district can still be 20% more co st-effective than full mainline electrification. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 27 Scenario Base Interm ittent Electri fication Conti nuous Electri fication Performance Measure Case Phase 1 Phase 2 Phase 3 Phase 4 Phase 1 Phase 2 Phase 3 Full Daily Train Miles: Electrified 0 5,920 13,280 18,680 21,280 7,240 13,560 24,360 39,990 Battery 0 1,720 7,460 9,680 9,080 0 0 0 0 Diesel 39,990 32,350 19,250 11,630 9,630 32,750 26,430 15,630 0 Total 39,990 39,990 39,990 39,990 39,990 39,990 39,990 39,990 39,990 (Diesel Ope rated Under the Wires) 0 1,880 760 680 80 1,880 80 80 0 Percentage of Train Miles: Electrified 0% 15% 33% 47% 53% 18% 34% 61% 100% Battery 0% 4% 19% 24% 23% 0% 0% 0% 0% Diesel 100% 81% 48% 29% 24% 82% 66% 39% 0% (% Electric Tracti on) 0% 19% 52% 71% 76% 18% 34% 61% 100% Active Fleet Requirements: Battery Electric 0 46 82 104 114 0 0 0 0 Straight Electric 0 0 0 0 10 40 98 105 132 Diesel 138 117 87 59 46 124 98 77 0 Total 138 163 169 163 170 164 196 182 132 Daily Engine Changes 0 20 12 18 24 24 72 48 0 Route Miles: Electrified 0 265 525 825 925 320 545 995 2,195 Not Electrified 2,195 1,930 1,670 1,370 1,270 1,875 1,650 1,200 0 Total 2,195 2,195 2,195 2,195 2,195 2,195 2,195 2,195 2,195 (% Electrified) 0% 12% 24% 38% 42% 15% 25% 45% 100% Investment Cost Estimate ($bn): . Electrification Infrastructure $0.00 $1.83 $3.63 $5.25 $6.17 $2.66 $4.26 $8.48 $16.74 Rolling Stock: Battery Electric $0.00 $0.46 $0.82 $1.04 $1.14 $0.00 $0.00 $0.00 $0.00 Straight Electric $0.00 $0.00 $0.00 $0.00 $0.06 $0.24 $0.59 $0.63 $1.01 Diesel $0.69 $0.59 $0.44 $0.29 $0.23 $0.62 $0.49 $0.39 $0.00 Total Locomotives $0.69 $1.04 $1.25 $1.34 $1.43 $0.86 $1.08 $1.01 $1.01 Total Investment $0.69 $2.87 $4.88 $6.59 $7.60 $3.52 $5.33 $9.49 $17.75 Cost Effectiveness: $ Investment per Annual Zero -Emission Train Mile N/A $1.25 $0.78 $0.77 $0.83 $1.62 $1.31 $1.30 $1.48 Annual Operating Costs ($m/annum): Maintenance of Way (Labor+Mat.): Signal Dept. $142.6 $147.1 $149.3 $151.7 $152.6 $148.2 $150.6 $155.3 $161.6 Communications Dept. $46.5 $46.8 $46.9 $47.1 $47.1 $46.8 $46.8 $47.2 $48.2 Electric Traction Dept. $0.0 $18.3 $32.9 $46.6 $52.3 $22.4 $34.2 $60.4 $112.5 Track & Structures Dept. $161.6 $164.2 $166.0 $168.3 $169.3 $165.2 $167.0 $170.6 $178.8 Total Maintenance of Way $350.7 $376.3 $395.2 $413.7 $421.4 $382.6 $398.6 $433.6 $501.1 Train & Engine ( Road Crews) $66.4 $71.1 $69.3 $70.7 $72.1 $72.1 $83.4 $77.8 $66.4 Fuel: Electric Power ($0.11/kWh) $0.0 $21.2 $57.6 $78.8 $85.0 $25.1 $47.1 $84.6 $138.9 Diesel ($6.00/gal) $569.8 $460.9 $274.3 $165.7 $137.2 $466.6 $376.6 $222.7 $0.0 Total Energy Cost $569.8 $482.2 $331.9 $244.5 $222.2 $491.8 $423.7 $307.3 $138.9 Affected Operating Expenses $986.9 $929.6 $796.4 $728.9 $715.7 $946.4 $905.7 $818.6 $706.5 Annual Savings versus Base Case $0.0 -$57.3 -$190.5 -$258.0 -$271.2 -$40.4 -$81.2 -$168.2 -$280.4 Net Present Value ($bn at 5%) $0.0 -$1.1 -$3.8 -$5.2 -$5.4 -$0.8 -$1.6 -$3.4 -$5.6 Shortfall vs. Base Case ($bn) N/A $1.7 $1.1 $1.4 $2.2 $2.7 $3.7 $6.1 $12.1 Table 5. Hypothetical North American Class I Case Study: Networ k Performance Metrics Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 28 (a) Relationship to Maintenance of Way Budget (b) Relationship to Operational Complexity 340360380400420440460480500 0% 20% 40% 60% 80% 100%Annual MOW Budget (Labour & Materials) $ Millions Percentage of Train Miles Under Electric TractionFull Electrification Intermittent Electrification Contiguous Electrification 01020304050607080 0% 20% 40% 60% 80% 100%Daily Engine Changes Percentage of Train Miles Under Electric TractionFull Electrification Intermittent Electrification Contiguous Electrification (c) Relationship to Investment Capital (d) Relationship to Investment Cost Effectiveness 02468101214161820 0% 20% 40% 60% 80% 100%Investment Capital (Fleet & Infrastructure) $ Billions Percentage of Train Miles Under Electric TractionFull Electrification Intermittent Electrification Contiguous Electrification $0.00$0.20$0.40$0.60$0.80$1.00$1.20$1.40$1.60$1.80 0% 20% 40% 60% 80% 100%Investment per Annual Zero -Emission Train Mile ($) Percentage of Train Miles Under Electric TractionFull Electrification Intermittent Electrification Contiguous Electrification Figure 16. Hypothetical North American Class I Electrification Case Study: Findings Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 29 Life Cycle Cost Analysis Figure 1 7 shows the total life cycle cost of for all scenarios outlined in Table 5. For all electrification scenarios, compared to a base scenario of diesel -only operations, the Net Present Value (NPV) of capital, operating, and maintenance costs are always higher in the electrification scenario under the current assumptions of energy costs. This explains why there has been little interest in electrification from the for -profit U.S. railroad industry. Lifecycle Cost Analysis (Sample Class I) $0$5$10$15$20$25$30$35 Base (B1) (B2) (B3) (B4) (C1) (C2) (C3) Full ScenarioLifecycle Cost ($ billions)E.T. Infra. Battery Locos Electric Locos Diesel Locos Signal MOW Comms MOW E.T. MOW T&S MOW T&E Crews Electric Power Diesel Fuel Scenarios: Base Case = Diesel Service Only B1-B4 = Intermittent + Battery Electric, Phases 1 thru 4 C1-C3 = Continuous Electrification, Phases 1 thru 3 Full = Total Mainline Electrification Discount Rate = 5%7.3%26.6%56.1% All Maintenance Costs are NPV. Figure 1 7. Life Cycle Cost Analysis for a Hypothetical North American Class I Railway The interesting finding here is that even with 76% of train -miles operated under electric traction in Scenario (B4) of intermittent electrific ation, the increase in lifecycle costs is only a modest 7.3%. However, the corresponding Scenario (C3) of continuous electrification delivers only 61% of electric train -miles for a cost increase of 26.6%, while the Full Electri fication Scenario results in a lifecycle cost increase of 56.1%. This further underscores the cost -effectiveness of BEL -enabled freight railroad electrification. SHORT TERM ACTIONS TOWARDS AN ELECTRIC FUTURE North American freight railroads have challenging operating environments with no recent electrification experience. To show Class I railroads that electrification is a mature technology, multiple areas need attention. Proving High -Capacity BELs Although 7.2 -MWh BELs have been announced, no prototypes exist as of this writing. 14.5 MWh combo -BELs are still at the concept stage. 2.4 -MWh BELs have proved out under service conditions (35). This development process should continue for high -capacity BELs. This work Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 30 would include identifying battery chemistry alternatives and val idating design assumptions , including those used in the present study . Perhaps a grant request for design, development , and construction of a small fleet of BELs using FRA Consolidated Rail Infrastructure and Safety Improvements (CRISI) Program funding could be considered . Demonstration Service on Existing Infrastructure For a demonstration in freight service once high -capacity BELs are available , the industry could consider o ne route from Harrisburg , Penn sylvania east to Perryville , Maryland , then north or south on the Northeast C orridor. This service is currently operated with diesel -electric locomotives with trains of less than 8,000 gross tons , with significant train -miles operated “under the wires” . Substituting BELs for diesel locomotives on such a service would initially take care of concern s regarding signal system and electric traction infrastructure compatibility , as the signal system and PTC are already in place. Clearances for Double -Stack Container Trains Electrification must accommodate Ame rican Association of Railroads (AAR) Plate H clearances, which apply to the tallest freights, double -stack container trains. India’s dedicated freight corridors (Figure 1 8) accommodate double -stack container trains under electric catenary (53), but differ ences in well -car designs, dynamic envelopes, wind parameters, and overpass/tunnel clearances require the technology to be proven locally. Figure 18. On Indian Railways, the Western Railway operates this electri fied double -stack container train fro m Palanpur to Botad in Gujarat, June 10, 2020; Piyush Goyal photo (Government of India Open Data License via http://indianrailways.gov.in/ ). Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 31 Demonstration programs are needed on high -volume intermodal corrido rs to gain operating and maintenance experience. Pantograph sway under freight operating conditions, with resulting dewirement risks, should be addressed and average reliability estimated based on such factors as prevailing wind speed, catenary design, su pport structure spacing, wire composition, pantograph specifications, wave propagation, speed and number of locomotives, track curvature, etc. Maximum safe speeds should also be established for different track classes. Pantograph sway issues at Plate H w ire height could make operation with OCS problematic at speeds over 100 mph ( 54 pp. 2 -3), potentially impacting nascent higher -speed passenger rail efforts. High and Wide Loads North American railroads pride themselves in supporting out -of-gauge dimensi onal loads such as aircraft fuselages, electrical components, and defense logistics items directly between rail - connected sites (55). Any electrification plans must take these needs into account, so that the necessary clearance profiles are provided ( 56 p. 14). Non -electrified routes or tracks must be identified if OCS would restrict th is very useful network capability. In areas with dense rail networks, a strategic set of lines could be designated for oversize loads. In some cases, additional -clearance OCS or parallel non -electrified tracks might be provided for high and wide loads. Analysis of Service Strategies : Tonnage and Terrain Due to the multiple -unit and remote -control capabilities of diesel -electric locomotives, and the substantial strength of AAR couplers, the train tonnage and horsepower required to move each train has grown virtually without limits over the past 30 years. This has led to increasing returns to scale within the industry, but the limits of AAR couplers have already been reache d and that operational strategy may be approaching a point of diminishing return s, where the risk of derailments or other incidents may exceed the cost of operating smaller trains. The financially feasible or fiscally prudent limits to supply substations power ratings may impose further restrictions on maximum train sizes, or indeed reduce the optimal average train size. To allow BEL -enabled electrification to be adopted on an industry -wide basis, an analysis of service strategies would be necessary to un derstand how or whether the industry may benefit from operating smaller trains more frequently. An understanding of this fundamental issue may lead to increased acceptance and buy -in for arbitrary maximum train length or tonnage limits for siding -length , substation -rating , and physical characteristics (terrain) related reason s. Analysis by Market Segment : Commodities and Speed One limitation of this current research is that although we estimated many variables using averages at a high level, we did not ev aluate the effect of market segments on BEL requirements or the length of “electric districts”. I ntermodal trains operate with significantly higher speeds and lighter loads than unit trains of bulk commodities, which may change the calculus regarding the fraction of route -miles needing electrification and the BEL specifications required . A logical next step would be to establish parameters for specific railroad franchises focused on different commodities. Effects of North American Climate North American climate conditions and geographical features challenge catenary maintenance: Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 32  Extreme cold, especially in Western Canada and the northern U.S. Plains states , where winter temperatures can occasionally be as low as –30°F, causes catenary wires to freeze (requiring deicing trains) or snap (insufficient slack to account for thermal contraction).  Extreme heat in the Southwest , where summer daytime temperatures reach 110°F, causing catenary wires to droop, and substation equipment to overheat.  Western wildfires may close segments of mainlines and force trains to be diverted onto other routes. This risk might be substantially mitigated through electrical grid improvements, as overheating is a significant cause of wildfires.  Atlantic Seaboard and Gulf Coast hurric anes, where between 2010 and 2021 an average of 7.8 hurricanes have occurred annually with sustained winds over 74 mph. These damage electrification infrastructure because of debris (trees, building components, etc.) falling on overhead line equipment .  Tornadoes, particularly in the Central U.S., are usually geographically limited in their impacts but can cause extreme damage.  Remote geography of the Rocky Mountains, high desert, and high plains , where routine maintenance access to railroad rights -of-way c an be challenging. Although technological solutions exist for these conditions, large -scale North American experience is insufficient to understand the maintenance cost implications of electrification. Demonstration programs in representative locales wou ld provide this necessary experience. Consequences of Electrification on Signal Systems Signal installations on m ost North American mainlines make no provision for future electrification. Current return on AC electrifications could cause interference w ith existing Signals and Communications circuits, due to ground leakage, negative return, and electromagnetic interference issues (see, e.g. (43)). Pilot projects working with different signal and control technologies could determine the likely impacts an d help develop mitigations. Potential Changes in Maintenance Practices Many Maintenance -of-Way processes would be impacted by electric catenary poles and wires. Aside from adding Electric Traction Departments and catenary inspection vehicles, some trac k maintenance methods would require modification, (e.g., cranes in switch replacement jobs, grapple trucks in tie jobs, signal inspections on overhead gantries, track and power outage procedures, etc.) Track time is already at a premium in very busy corri dors, and the maintenance productivity impacts of working in an OCS environment must be addressed (51). High -clearance OCS may mitigate, but not eliminate these challenges. Demonstration projects will help develop safety procedures, and gain informatio n and operating experience. It would also be useful to review experience with electrifications, past and present, involving heavy freight service to determine what elements of their construction (choice of design and materials) and maintenance might infor m railroads going forward. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 33 Catenary Zigzag Early 20th century electrifications generally sought to keep overhead wires at or near track centerline. Most railroads used short tangent sections on curves to prevent pantographs from dewiring and fouling ha nger wires ( 57 p. 179 -183). The Pennsylvania Railroad superelevated much of its catenary work to keep contact wires centered relative to pantographs ( 58 pp. 26 -29). With the increased use of constant -tension catenary involving sections about a mile long, held taut with counterweights or springs, it is accepted that OCS zigzag is necessary and even desirable to distribute wear more evenly along pantograph contact strips. But North American experience with OCS zigzag is based on passenger experience. Tole rances for freight operation s will need to be established. Opportunities for Federal Assistance These challenges should be addressed with suitably funded Federal demonstration programs covering operating and maintenance experience, best practices in desig n, construction, and maintenance, and cost implications. Demonstration programs should cover multiple sites in various geographies. The U.S. federal government has historically been heavily involved in railroad electrification. The largest U.S. electrif ication project to date (the Pennsylvania Railroad’s electrification from Wilmington, Delaware to Washington, D.C. and from Paoli to Harrisburg, Pennsylvania) was funded by Works Progress Administration loans during the Depression (59 pp. 141 -165). Indeed , the seminal Gibbs & Hill Conrail electrification feasibility study , discussed in (43,60 pp. 30-35), was completed in response to the 1976 Railroad Revitalization and Regulatory Reform (4R) Act’s Section 606(i) requirements. Railroad, electric utility, a nd public officials could use updated guidance similar to that offered in 1977 with TRB Special Report 180, Railroad Electrification: The Issues (61). Similarly, British Railways hosted a conference in 1960 to promote 25kV commercial -frequency AC electrif ication (62), hitherto implemented only in France. Industry -Driven Legislative Guide From the private sector perspective, there may be a need to produce a legislative guide. With a public works project of this magnitude and expected benefits shared bet ween privately owned railroads and the public realm, the industry should define the terms of engagement and the types of government grant programmes or incentives that it would like to see. Such a study could elicit reasons why railroads might resist such programs , and possible roadblocks ( e.g., addit ional social, unrelated political requirements) , that if included in legislation, might hinder industry involvement and buy -in. This could aid lawmakers in developing funding, requirements, and legislation. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 34 LONGER TERM IMPLEMENTATION ANALYSIS AND PLANNING In parallel with short -term actions, steps could be taken to determine how a catenary electrification system might be built out : Commodity Flow Analysis: Where to Build Planning future electrification requ ires more than simply looking at present -day traffic flows (63). Dominant freight traffic flows would change with future reductions in fossil fuel use and trends towards re -shoring manufacturing. Traffic flow data are needed to determine engineering parameters and lines to electrify. Thus, full future commodity flow studies should be undertaken. Such strategic analyses were last conducted in earnest for parts of the U.S., funded by the 1973 Regional Rail Reorganization Act (64,65). This function has pa ssed onto state rail plans, but these rarely address systemwide issues, which must be considered when deciding where to electrify, with what technology, with which operating strategy, in what sequence. Analyses using such data sources as the STB Rail Wa ybill Sample, U.S. Census Commodity Flow Survey, their Canadian equivalents, private databases of commodity -level truck traffic forecasts, and nationwide economic forecast models with multiple industrial development scenarios are needed to inform preferred locations for electrification pilot projects. Such commodity flow analyses would also identify industrial segments potentially benefitting from federal investments and could generate or identify constituencies favo uring demonstration projects. Similar m ethods have been applied to publicly funded rail freight investment projects (66). Business Case Analysis: Why Build The North American rail industry has multiple stakeholders with competing interests. Electrification programs must show benefits from eac h stakeholder’s perspective, including electric utilities, freight railroads, intercity passenger carriers, commuter railroads, and the public interest. Business case analyses can show anticipated benefits accruing to all stakeholders and may offer guidan ce for cost allocation so the project investment burden can be shared equitably. Methods used by the Northeast Corridor Commission show that, with the right legislative framework, Federal quangos ( quasi non -governmental organizations ) can implement arrang ements to distribute investment burdens among competing interests, and account for non - monetary contributions (67). Federal demonstration programs could include a National Rail Electrification Planning Commission to perform business case analyses and ensu re investment program areas are sustainable with good cost -benefit ratios. It could also spearhead strategic system planning and coordinate demonstration projects. Electrification System Strategic Planning: What to Build Switching from fossil fuel -power ed to electric vehicles will require enormous upgrades to electrical grids. Policymakers and utility officials must take freight railroads’ needs into account when planning these upgrades. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 35 An electrified railroad has peaky single -phase loads. Joint plan ning must take place with local utilities to manage their impacts. However, the linear nature of rail lines means that railroads can acquire power from cheaper sources enroute with transmission or even co -located generation investments like solar farms, w ind farms, and hydroelectricity, although load balancing with local grids will still be needed. Here, BELs provide another advantage by buffering peaky loads, a goal which electrified railroads have long pursued (68). Smaller electrification projects can involve cost minimization whilst meet ing specifications. But here, strategic railroad -and-transmission grid interconnection points c an be identified, and high traffic -density electrified corridors grown organically outwards as far as train traffic and po wer transmission limits justify. This also identifies “power gaps” for planning future generation or transmission capacity, together with interim “diesel plans” or hydrogen alternatives for line segments deemed uneconomical to electrify at present , even w ith the infrastructure savings available from BELs . Unlike straight electrics, BELs can traverse such elements as truss bridges, movable bridges, tunnels, and constricted -clearance overpasses in battery mode, making it unnecessary to electrify there (with consequent capital savings from not having to raise clearances) . These geographical barriers often form natural boundaries for electricity distribution zones. By leaving them unelectrified, complex electrical switching arrangements can be avoided. System plans identifying line segments worth electrifying from both traffic and power availability perspectives also allow utilities to plan generation and transmission capacity by identifying future electrified railway demands, providing valuable information including load size, characteristics, and grid connection points. In addition to the direct costs, an OCS imposes indirect costs by constraining track geometry, which raises curve realignment and track superelevation costs for higher speeds. Several lin es are being studied for incremental higher -speed passenger service s at up to 125 mph. Such investments should be considered together with freight needs and sequenced appropriately. Federal demonstration programs could include nationwide planning studies , divided into regions, using results from technological proof -of-concept, operations strategy, and commodity flow analysis to provide long -term blueprints for North American mainline railroad electrification. Institutional Mechanisms: How to Pay The Asso ciation of American Railroads is opposed to electrification, particularly because of the capital cost (69). If moving toward carbon -neutral transportation is an important policy goal, governments should be prepared to finance non -emitting technologies, an d help railroads make the transition . Several ideas follow:  A Class One railroad president suggested in 2008 that electrification might be funded through tax credits (70). This could incentivize railroads to make large, socially desirable investments ba sed on enlightened self -interest.  Railroads might consider joint ventures with consortia, perhaps “a mix of financial institutions, including insurance companies, banks, and pension funds. Depending on the Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 36 location of the proposed project, … a development authority might also be pursued” (71 p. 50) .  For smaller railroads, governments could make infrastructure improvement loans (like Railroad Rehabilitation and Improvement Financing) or grants, using evaluation criteria like the Federal Transit Administrati on’s for evaluating trips carried per amount invested, and allowing local matches. Thus, railroads would state how many ton -miles would be electrically hauled and how much GHG emissions eliminated (including electric generation), using models like Canada’ s GHGenius.  In 2009, responding to the Great Recession, U .S. Congress instituted the Car Allowance Rebate System, better known as the “cash -for-clunkers” program, which reduced emissions from private automobiles. Similar programs could help railroads affo rd non - emitting locomotives. Where traffic levels are too low to justify electrification, it could incentivize railroads to convert to battery or hydrogen power.  Under a cap -and-trade regime, firms in industries that cannot shift to GHG -free activities seek to buy GHG emission rights from other firms —potentially including railroads. This could provide funds to reduce railroad emissions. Obviously, it should be priced correctly so that electric utilities would not purchase credits to operate coal -fired pl ants to generate power for railroad electrification.  Closing inter -line electrification “gaps” at major gateways was formerly a concern for electrification planning. With BELs, though, this is less important , as locomotives can switch readily between elec tric and battery modes (assuming sufficient electrical charge). Nevertheless, since battery recharging is time -dependent, installing OCS on busier parts of major terminal railroads (e.g., Conrail Shared Assets, Belt Railway of Chicago, Indiana Harbor Belt , Terminal Railroad Association of St. Louis) might provide operating efficiencies by allowing BELs to recharge while waiting for clearance to proceed through congested areas .  AAR has standards on how railroads may charge each other for working on each o ther’s rolling stock, whether out of necessity or for mutual benefit. A similar system would be needed for electric power charges, perhaps like the norms for wholesale purchase of electricity by one utility company from another. Auditable net -use meters on BELs could show whose units are consuming how much power on which railroad, when, and for what purpose (e.g., propulsion, battery charging, regeneration). This information would also be internally useful as railroads deploy real -time throttle optimizat ion tools. Differences From Prior Efforts Rail freight electrification for carbon neutrality will differ in two significant ways from earlier proposals based on attaining energy independence ( 72,73). First, those proposals envisioned electrification from the Powder River Basin in eastern Wyoming (North America’s leading source of coal) and may have also presumed electric haulage of Appalachian coal traffic. Those priorities are no longer in keeping with public policy. North American free trade and cross -border railway mergers and acquisitions will create a cross - border electrified network, and Canadian systems may well center on Chicago like their U .S. counterparts. Mexican railroads may eventually become part of this electrified network. Intermittent Electrification w ith Battery Locomotives and the Lu and Allen Post-Diesel Future of North American Freight Railroads 37 CONCLUSION Freight railroads are understandably concerned about the cost of finding alternatives to diesel - electric traction. But if public policy (and lasting changes in the price and supply of petroleum) move North America’s railroads towards non -emitting propulsi on technologies, this research shows discontinuous or intermittent electrification with BELs supplemented with cabless boosters for energy storage, alternating approximately every 200 miles between powered and unpowered segments, is a doable approach with technological promise and high cost - effectiveness, provided that the energy capacity, charging rate, weight characteristics, and reliability of BELs are proven in practical service conditions. ACKNOWLEDGEMENTS The authors thank Robert Newhouser, J.E. Kes ich, Walter Simpson, Stu Trout, Alla Reddy , and Steve Vitoff for reviewing an earlier version of this work , as well as many anonymous referees who provided good advice and suggested many improvements for prior versions of this manuscript . Additionally, L. Brown, D. Godard, S. Whitman, P. Zhong , S. Ross, and J. Benson provided especially helpful discussion. T. Fitzpatrick provided excellent graphic arts services. The views are those of the authors and do not necessarily reflect the official policy of any railroads, manufacturers, government bodies, or any other organizations.