Driving Brake Standard Open
The Driving Brake Standard Open (DBSO) is a specialized type of railway control car developed for British Rail, converted from Mark 2F Brake Standard Open (BSO) passenger coaches to enable push-pull train operations without requiring the locomotive to run around the train at terminals.[1] These conversions incorporated a driving cab equipped with through-train dispatch multiple-unit (TDM) control systems at one end, allowing the train to be driven from the trailing coach, alongside a guard's brake compartment and open-plan saloon seating for 32 standard-class passengers.[1] Measuring 20.12 meters in length, 2.82 meters in width, and weighing approximately 33.5 tonnes, DBSOs were designed for compatibility with air-braked rolling stock and Class 47 locomotives, distinguishing them from driving van trailers (DVTs) used in high-speed InterCity services.[1] The DBSO fleet originated in the late 1970s as part of British Rail's efforts to improve efficiency on key commuter routes, with the first conversions undertaken at Glasgow Works from 1974-built Mk2F BSOs starting in 1979.[2] A batch of ten vehicles (numbered 9701–9710) entered service on October 22, 1979, for push-pull operations between Glasgow and Edinburgh using modified Class 47/7 locomotives, followed by four more (9711–9714) in 1985–1986 for extensions to Aberdeen and other Scottish lines.[2] By 1984, the fleet had been repainted in ScotRail Express livery, but the Polmont rail disaster that year destroyed unit 9706 and prompted safety upgrades, including reinforced front-end protection and obstacle deflectors on all survivors.[2] With the introduction of Class 158 diesel multiple units, DBSOs were withdrawn from Scottish services by June 1990 and overhauled at Derby Etches Park before redeployment to East Anglia for Anglia Railways' Norwich–London Liverpool Street workings, where they operated until 2005–2007.[2] Several units were later repurposed for departmental use by Network Rail as rail traffic observation vehicles (RTOVs) or engineering support coaches, while others entered preservation, such as former SC9712 (renumbered 8918) at the Downpatrick and County Down Railway, which was regauged to 5 ft 3 in Irish broad gauge and restored for heritage operations.[3] As of 2025, several DBSOs remain in use for departmental purposes by Network Rail and in preservation. Today, surviving DBSOs represent a notable example of British Rail's adaptive engineering for regional passenger services, with their push-pull capabilities influencing later control car designs.[2][4]History
Development and conversion
In the 1970s, British Rail sought to enhance operational efficiency on key intercity routes, such as the Glasgow-Edinburgh line, by adopting push-pull train configurations that allowed locomotives to remain at one end of the consist without requiring time-consuming runarounds at terminals. This approach avoided the need for full multiple-unit formations while reducing crew requirements and locomotive repositioning, thereby improving turnaround times and capacity utilization on busy corridors.[5][2] The conversion program for Driving Brake Standard Open (DBSO) vehicles commenced in 1979 at Glasgow Works, where standard Mark 2F Brake Standard Open (BSO) coaches were rebuilt into control trailers. The initial batch comprised 10 units, numbered 9701-9710, which underwent trials starting in August 1979 before entering service later that year. These conversions transformed existing brake coaches by installing a half-cab structure at the brake end, incorporating an EMU-style power controller, and integrating a Brush two-wire push-pull control system that utilized the standard Railway Clearing House (RCH) jumper cables for remote locomotive operation. The process also involved retaining cab-end gangway connections but covering them with a wooden panel to accommodate the new driving position.[2][5] A second batch of four additional DBSOs (9711-9714) was produced between 1985 and 1986 to support service expansions, including on the Glasgow-Aberdeen route, following the success of the original set. The rebuilding rationale centered on cost-effective retrofitting of proven Mark 2 stock to enable bidirectional working, thereby minimizing infrastructure changes and capital expenditure compared to procuring new dedicated multiple units. Post-conversion modifications, such as the addition of obstacle deflectors beneath the buffer beam in response to the 1984 Polmont derailment, further refined safety without altering the core control architecture.[2]Introduction to service
The Driving Brake Standard Open (DBSO) vehicles entered revenue service on 22 October 1979, debuting on the Glasgow-Edinburgh route via Falkirk High with Class 47/7 locomotives in push-pull configuration, where the DBSO led the train and the locomotive provided propulsion from the rear.[2] This setup replaced earlier Class 27 push-pull operations by February 1980 and enabled efficient operation without the need for the locomotive to run around the train at terminals.[2] The DBSOs, converted from Mark 2f Brake Standard Open coaches, featured a driving cab at one end for remote control of the locomotive, with seating for 32 second-class passengers in an open saloon layout, alongside brake equipment and a guard's compartment.[5] Typical formations consisted of the DBSO at the Glasgow end, followed by Mark 3 standard open and buffet coaches, and the Class 47/7 locomotive at the Edinburgh end, supporting 100 mph running on upgraded infrastructure.[2] From April 1981, sets incorporated a Mark 1 buffet car for enhanced passenger amenities. Early operations faced challenges in integrating the push-pull system with existing signaling, requiring adaptations to ensure reliable train control, and necessitated specialized driver training for the DBSO's cab interfaces and remote locomotive handling.[5] A notable early incident occurred on 30 July 1984 near Polmont, where DBSO 9706 leading an Edinburgh-Glasgow push-pull train struck a cow at approximately 85 mph, resulting in derailment, 13 fatalities, and multiple injuries; the official investigation report emphasized trackside access vulnerabilities but prompted safety enhancements for DBSO-led trains.[6] In response, obstacle deflectors were fitted beneath the leading buffer beams of the DBSO fleet starting in March 1985.[2] By the end of 1985, 12 DBSOs were operational for ScotRail InterCity services, with additional conversions (9711–9714, with 9711–9713 in 1985) enabling extensions to the Glasgow-Aberdeen route using Mark 2d intermediate stock from May onward, which supported increased service frequency to hourly intervals on the core Glasgow-Edinburgh corridor.[2]Design and technical specifications
Construction and modifications
The Driving Brake Standard Open (DBSO) coaches were derived from existing Brake Standard Open (BSO) carriages, primarily Mark 2 variants, through structural modifications that included the addition of a driving cab while retaining the core body shell. The base BSO coaches measured 66 ft 0 in (20.12 m) in length over buffers and 9 ft 3 in (2.82 m) in width, weighing approximately 33.5 tonnes, constructed with a steel body and semi-integral underframe designed for enhanced strength. These coaches were mounted on B4 bogies for later Mark 2 builds, though some conversions utilized Commonwealth bogies equipped with air suspension to achieve a maximum speed of 100 mph (161 km/h).[7] Modifications during conversion preserved the open saloon layout with 32 standard class seats in a 2+2 configuration across the passenger area, alongside a guard's compartment approximately 16 ft in length and a dedicated luggage area for operational flexibility.[3] Additional alterations included the installation of a through corridor connection at the cab end and Electric Train Heating (ETH) jumpers to facilitate push-pull operations with locomotives. The underframe was strengthened with additional steel reinforcements to support the cab mounting without compromising the overall structural integrity.[5] The braking system was upgraded to electro-pneumatic (EP) air brakes as the primary mechanism, with a vacuum fallback provision for compatibility with mixed stock.[8] Initially painted in BR blue and grey, many DBSOs were later repainted in ScotRail Express or Regional Railways blue and grey for provincial services.[3]Driving cab and control systems
The driving cab of the Driving Brake Standard Open (DBSO) is installed at one end of the converted Mark 2 coach, providing a dedicated space for remote operation of the train in push-pull configuration. It features a full-width driving desk equipped with essential controls, including a deadman's handle for driver vigilance and the Automatic Warning System (AWS) to alert the driver of signal aspects. Later modifications incorporated the Train Protection and Warning System (TPWS) to enhance signal-pass reading and overspeed prevention, ensuring compliance with modern safety standards for control cars.[9] Control linkages in the DBSO utilize Time Division Multiplex (TDM) cabling to transmit signals for the locomotive's throttle, brakes, and AWS from the cab to the lead locomotive, supporting operations up to nine coaches distant. This system employs frequency modulation over existing carriage lighting circuits and Railway Clearing House (RCH) jumper cables, enabling compatibility primarily with Class 47/7 locomotives, with later adaptations for other classes such as 31 and 37.[2] The TDM setup allows seamless multiple working without the need for the locomotive to lead, improving operational flexibility on diesel lines.[10] Visibility from the cab is optimized with forward-facing windows and a design height of 15 feet 6 inches, facilitating clear sightlines for signaling and route navigation, supplemented by radio communication for driver-to-signaler interactions. Original builds lacked Automatic Train Protection (ATP), relying instead on AWS and manual vigilance, though ergonomic considerations in the desk layout minimize driver fatigue during extended runs.[11] Following the 1984 Polmont rail accident involving a DBSO, which highlighted issues in remote braking response times, the 1985 conversion batch received safety upgrades including reinforced front-end protection and obstacle deflectors on all survivors. These modifications addressed vulnerabilities in push-pull dynamics, such as signal propagation delays in the TDM system, without altering the core cab structure.[6]Operations
Initial deployment
The Driving Brake Standard Open (DBSO) vehicles saw their initial extensive deployment on the Edinburgh–Glasgow route via Falkirk under the ScotRail brand starting in the late 1970s. Trials began in August 1979, with the inaugural passenger service running on 22 October 1979 behind Class 47/7 locomotive 47709, and full implementation achieved by February 1980. These operations utilized formations typically comprising a Class 47/7 locomotive (such as 47701–47717), 5–7 Mk3 coaches, and a DBSO in push-pull configuration, enabling services to reach speeds of 100 mph and reduce journey times compared to previous workings.[2][12] Operator transitions marked the evolving use of DBSOs during this period, shifting from ScotRail management in the 1980s on Scottish services to Anglia Railways following British Rail privatisation in 1997, which introduced refurbished interiors to the fleet for enhanced passenger comfort on the Great Eastern services.[13][14]Later uses and withdrawals
In the 1990s, DBSOs were withdrawn from ScotRail operations as part of a shift toward more modern multiple units and electrification initiatives on key routes. The introduction of Class 158 DMUs replaced the push-pull formations on services such as Glasgow-Edinburgh, leading to the transfer of the fleet in 1990 under British Rail's InterCity sector for use on London Liverpool Street to Norwich workings. From 1990 to 1997, the DBSOs were used on London Liverpool Street–Norwich services under British Rail's InterCity sector, paired with Class 90 electric locomotives and 8–10 Mk2 coaches. These formations typically formed 12-car trains with the locomotive at the front and DBSO at the rear, primarily for peak-hour expresses accommodating over 500 passengers. The DBSOs' cab control systems ensured compatibility with the locomotives' through-cable connections for remote operation from the rear.[2][5][15] During the Anglia Railways franchise from 1997 to 2004, and subsequently under National Express East Anglia until 2006, the DBSOs operated in push-pull configuration with Class 86 and Class 90 locomotives (and occasionally Class 47 diesels) on Norwich services, but the aging vehicles suffered from reliability issues related to their converted design and maintenance challenges. These problems prompted a transition to more robust Driving Van Trailers (DVTs) cascaded from other operators, paired with Mark 3 coaches for improved performance.[5][7] The DBSOs saw their final passenger operations under National Express East Anglia in December 2006, marking the end of mainline service for the type, after which the remaining fleet was stored at Bounds Green depot.[5] Post-withdrawal, several DBSOs found alternative roles in the charter sector, including use by Locomotive Services Limited to recreate 1980s ScotRail push-pull sets for heritage tours. From 2010 onward, Network Rail repurposed others for departmental duties, such as remote-operated test trains including ultrasonic rail inspection formations. As of 2025, surviving DBSOs continue in heritage operations, such as with Locomotive Services Limited recreating ScotRail push-pull sets, and departmental use by Network Rail.[10][16][17]Fleet status
Active and preserved vehicles
As of November 2025, five Driving Brake Standard Open (DBSO) coaches remain in active service with Network Rail for infrastructure testing and remote train operations. These vehicles are used as control cars on test trains, enabling push-pull configurations without a leading locomotive. The active units are 9701, 9702, 9703, 9708, and 9714, all based primarily at Derby RTC or Doncaster and painted in Network Rail's yellow research livery. Recent sightings include 9701 at Derby on January 2, 2025; 9703 on test runs in October and November 2025 with Colas Class 37 locomotives; 9708 at Eastleigh on January 18, 2025, and Rochester in July 2025; and 9714 at Crewe in October 2025 and on the Medway Valley Line in May 2025.[18][19][20][17] Seven DBSOs are preserved and operational (or held for future use) with heritage and charter operators, supporting push-pull formations on mainline railtours and preserved railways. Eastern Rail Services maintains DBSOs 9705, 9709, and 9710 at its Great Yarmouth depot for charter operations, having acquired them from Direct Rail Services in 2022 after overhauls.[21][22] Locomotive Services Limited operates DBSOs 9704 and 9707 as part of a recreated 1980s ScotRail push-pull set based at Crewe, paired with Class 47 locomotive 47712 for mainline railtours; these were added to the fleet in 2022 and have been used on Scottish routes in 2023–2025.[10] DBSO 9711 is preserved at Crewe Heritage Centre by the Crewe Diesel Preservation Group, intended for future use with Class 47/7 47712, though currently static.[10] Additionally, DBSO 8918 (formerly 9712) operates at the Downpatrick and County Down Railway since 2018, serving as a control vehicle and compatibility translator in a buffet set with a Class 450 railcar.[3]| Vehicle Number | Operator | Role | Status (November 2025) |
|---|---|---|---|
| 9701 | Network Rail | Infrastructure test trains | Active, based at Doncaster/Derby |
| 9702 | Network Rail | Infrastructure test trains | Active, based at Derby RTC |
| 9703 | Network Rail | Infrastructure test trains | Active, used in 2025 test runs |
| 9705 | Eastern Rail Services | Charters | Preserved and operational, based at Great Yarmouth |
| 9704 | Locomotive Services Limited | Charter push-pull set | Active, based at Crewe |
| 9707 | Locomotive Services Limited | Charter push-pull set | Active, based at Crewe; used in railtours |
| 9708 | Network Rail | Infrastructure test trains (gauging/RTOV) | Active, based at Derby |
| 9709 | Eastern Rail Services | Charters | Preserved and operational |
| 9710 | Eastern Rail Services | Charters | Preserved and operational |
| 9711 | Crewe Diesel Preservation Group | Preservation (future push-pull) | Preserved, static at Crewe Heritage Centre |
| 9714 | Network Rail | Infrastructure test trains | Active, based at Derby |
| 8918 (ex-9712) | Downpatrick and County Down Railway | Heritage services | Operational |