Thomas Saf-T-Liner C2

The Thomas Saf-T-Liner C2 (often shortened to Thomas C2) is a cowled-chassis bus manufactured by bus body manufacturer Thomas Built Buses. Introduced in 2004, the C2 marked the first usage of the Freightliner C2 chassis. While produced largely for school bus use, the C2 is also produced for multiple applications, including specialty and commercial configurations. The C2 is unique in that it is available in capacities up to 81 passengers, the largest of any type C conventional school bus in current production.[1]

Thomas Saf-T-Liner C2
Southwest Coach 2984 side.jpg
Front 3/4 view
ManufacturerThomas Built Buses (Freightliner)
AssemblyHigh Point, North Carolina
Body and chassis
ChassisFreightliner M2
RelatedFreightliner M2 106
  • Diesel
    • Cummins ISB 200-260hp (2008-present; CNG option since 2016)
    • Caterpillar C7 (2004-2007)
    • Detroit Diesel DD5 5.1 L I4 (2018-present)
    • Mercedes-Benz MBE 900 (2004-2007)
  • Propane
    • Powertrain Integration PIthon 8.0 L V8 (2014-present)
Width96 in (2,438 mm)
Curb weight18,000–35,000 lb (8,165–15,876 kg) (GVWR)

Derived from the Freightliner Business Class M2 medium-duty truck, the C2 consolidated the Saf-T-Liner Conventional and Saf-T-Liner FS-65 conventionals; the latter was produced concurrently with the C2 until December 2006.[2] While produced with a full-length hood, the C2 adopted other design elements of the Vista conventional to improve loading-zone visibility.

Thomas Built Buses manufactures the C2 in High Point, North Carolina.[3]


Thomas Saf-T-Liner FS-65, predecessor of the Saf-T-Liner C2

Following the introduction of the Freightliner Business Class M2 medium-duty truck in 2002 as the replacement for the FL-Series, Freightliner began work on an all-new bus chassis based on the M2 to replace the FS-65 bus chassis. As the parent company of Thomas Built Buses, Freightliner sought to pair the new bus chassis together with a new Thomas body, allowing the bus company to update its Saf-T-Liner Conventional bus body for the first time since 1962.

In 2004, in preparation for the C2, Thomas completed construction on a second production facility in High Point, North Carolina, adding 275,000 square feet of production capability.[3] Following the introduction of the C2, its Saf-T-Liner FS-65 predecessor remained in production through the end of 2006, outliving the medium-duty FL-Series by nearly three years.

In October 2012, Thomas delivered its 50,000th Saf-T-Liner C2 to Dean Transportation of Lansing, Michigan.

In June 2018, the 100,000th Thomas Saf-T-Liner C2 was delivered to Montgomery County Public Schools in Virginia.[4]


2013 Thomas Saf-T-Liner C2 in Virginia

Design and manufactureEdit

As the Thomas Saf-T-Liner C2 marked the first completely new bus body for the company since 1962, Thomas redesigned a number of its manufacturing techniques coinciding with its introduction.

To minimize the number of rivets and welds (a weak point of structural integrity on a bus body), adhesive bonding was used to complete a number of body joints. In the cases where fasteners are needed, self-piercing rivets are used. These engineered fasteners join layers of metal together without punching completely through the bottom layer, thus reducing the likelihood that rivets will become the source of leaks in the future.

To simplify vehicle maintenance, the electrical system of the C2 was redesigned over previous buses. In place of individually wired circuits, the C2 uses multiplexed wiring. With the system, switches on interior control panels can be removed and rearranged to suit the driver without any rewiring or reprogramming.


Cummins ISB6.7 in a Saf-T-Liner C2

As with all conventional-style school buses, the C2 is derived from a cowled-chassis conventional; the C2 uses the Freightliner C2 variant of the M2. As with 2000s and 2010s industry practice in school bus manufacturing, chassis and body manufacturers are paired, with Freightliner and Thomas developing the C2 as an integrated vehicle (the Freightliner grille badges are replaced with Thomas badges).

At its launch, Mercedes-Benz MBE diesel engines were the standard engines, with optional Caterpillar C7 and Cummins ISB diesels. In 2008, the Cummins ISB6.7 replaced the MBE900 as the standard engine, with the C7 discontinued. From 2010 to 2018, the sole diesel engine in the Thomas C2 was the Cummins ISB6.7; for 2018 production, the Detroit Diesel DD5 becomes an option.[5]

The C2 comes standard with an Allison 2500 automatic transmission with an Allison 3000 automatic transmission as an option. The Saf-T-Liner C2 is the only school bus in North America offered with a manual transmission; a rarely ordered option is a Fuller 6-speed transmission.

Engine Configuration Fuel Notes Transmission
Caterpillar C7 7.2 L (441 cu in) turbo I6 diesel optional engine, discontinued after 2008 Allison 2500 automatic

Allison 3000 automatic

Fuller 6-speed manual

Cummins ISB6.7 6.7 L (409 cu in) turbo I6 diesel


available 2009-present; produced with diesel-electric powertrain from 2009 to 2013
Detroit Diesel DD5 5.1 L (313 cu in) turbo I4 diesel optional engine, entering production 2018
Mercedes-Benz MBE900 4.2 L (259 cu in) turbo I4 (MBE904) diesel standard engine at launch, discontinued after 2009
4.8 L (293 cu in) turbo I4 (MBE924)
6.4 L (388 cu in) turbo I6 (MBE906)
7.2 L (438 cu in) turbo I6 (MBE926)
Powertrain Integration PIthon 8.0 L (487 cu in) OHV V8 propane/LPG Gasoline available 2014–2018
Power Solutions International DriveForce 8.8 L (535 cu in) OHV V8 available 2019–present
Proterra ProDrive Permanent magnet motor battery electric offered from 2019 Proterra 2-speed automatic


Rear view, Thomas Saf-T-Liner C2 (2004-2007)

In a break from traditional bus body design, as body manufacturers acted as second stage manufacturers adapting the body to the chassis, in the design of the C2, Freightliner-owned Thomas Built Buses designed the body and chassis of Saf-T-Liner C2 as fully integrated components. A separate body from the Saf-T-Liner EFX/HDX and Minotour, the C2 body shares no parts with its Saf-T-Liner Conventional/FS-65 predecessor.

While Freightliner has also produced cutaway-cab buses derived from the M2 for commercial/transit use, Thomas Built Buses is the only manufacturer to produce a cowled-chassis bus body derived from the M2. Coinciding with the shift to the Freightliner M2 cowl, several changes were made to improve the functionality over its predecessor. Most visibly, to improve aerodynamics, the traditional multipane vertical windshield was replaced by a sloped single-piece curved piece of glass (allowing the use of the stock windshield wipers).[6] Above the windshield, the front bodywork matches the windshield slope; to further improve aerodynamics, the warning lamp lenses are faired into the body (where allowed by regulations).

On the rear of the C2, the body also used flush-mounted glass and warning-lamp lenses. While not substantially physically taller than its predecessor, Thomas visually extended the height of the C2 with larger passenger windows than previous school buses, along with larger exit doors.

On the exterior, the C2 has largely remained the same throughout its production run. In late 2007, the passenger windows saw a minor change, with a shift to equal-size window sashes (previously, the top half was larger). In the rear, the taillights were redesigned and enlarged, later becoming a standard design for all Thomas buses. To improve driver sightlines, the mirror bracket for the passenger-side rear-view mirrors was extended forward.

In the interior of the C2, Thomas made many advancements in an effort to maximize parts compatibility between the bus body and donor chassis. In previous conventional-style school buses, from the firewall rearward, only the steering column and instrument cluster were used. With the interior of the Thomas C2, the dashboard of Freightliner M2 is used in its entirety, adopting only minor changes (the ignition switch was required to move to the center of the dashboard, due to a driver control panel replacing the driver-side door).

Along with the optimization of aerodynamics, the body of the Thomas C2 also optimized driver visibility. Following the redesign of the windshield, the entry door was repositioned, creating a large window between the entry door and windshield to view sightlines in the loading zone (a feature adopted from the Thomas Vista and nearly all small school buses); a smaller quarter window was located forward of the driver's sliding window. In comparison to other Thomas buses, the C2 has enlarged passenger windows and larger emergency exits.[7]

While initially equipped with an air-operated entry door, in 2012, an electric-operated entry door became offered as an option. Since 2016, a manually operated passenger entry door was added as an option.[citation needed]


2018 "Jouley" prototype, electric-powered Thomas Saf-T-Liner C2 school bus

Other usesEdit

Alongside its yellow school bus configuration, Thomas Built Buses produces multiple configurations of the Saf-T-Liner C2, including MFSAB versions (activity/childcare versions), along with the Transit Liner C2 commercial-use bus. Through aftermarket manufacturers, the C2 also serves as a donor vehicle for multiple types of specialty vehicles derived from bus bodies.[8]

Alternative fuel, hybrid, and electric powertrainsEdit

In 2007, Thomas introduced a hybrid-electric version of the Saf-T-Liner, named the C2e (stylized as C2e). The parallel hybrid drivetrain was designed by Eaton Corporation; the C2e retains the Cummins ISB engine and adds a 1.9 kW-hr lithium-ion battery pack with a 44 kW electric motor/generator.[9][10][11] Annual fuel savings were estimated to range from 300 to 450 US gal (1,100 to 1,700 l) assuming 10,000 miles (16,000 km) per year.[12][13] This is a 20% increase in fuel economy, and the buses can drive under battery propulsion for up to 15 miles (24 km).[14] At least 24 C2e buses were built and delivered to operators in Kentucky and Michigan.[14][15] In the summer of 2013, Thomas removed the C2e product literature from their website, marking its discontinuation.

In May 2014, Thomas Built Buses began production of a propane-fueled version of the Saf-T-Liner C2.[16] Powered by a 339 hp 8.0L V8, the C2 Propane is paired with the Allison 2300PTS automatic transmission.[17] The engine is designed by Powertrain Integration (an OEM supplier to General Motors) with the 8.0L V8 named the PIthon.[18][19] In 2019, the propane engine was enlarged to a DriveForce-branded 8.8 L,[20] supplied by Power Solutions International,[21] which had acquired Powertrain Integration in 2015.[22]

In 2016, a compressed natural gas (CNG) variant of the Saf-T-Liner C2 was released. The first Type C (conventional-style) school bus produced with a CNG fuel system, the Saf-T-Liner C2 CNG is powered by a version of the Cummins ISB 6.7 engine.[23]

In November 2018, Thomas unveiled a battery-powered prototype of the Thomas Saf-T-Liner C2 designated eC2 or "Jouley" (after the unit of energy).[24] The prototype previews an all-electric C2 intended for production during 2019;[25] it was developed in partnership with Proterra, Inc., who offer a line of transit buses using the same battery-electric drivetrain.[26] The C2 Jouley uses a single traction motor with an output of 295 / 170 hp (220 / 127 kW) (peak/continuous) and a two-speed gearbox; this configuration is branded ProDrive by Proterra. The traction battery has a total capacity of 220 kW-hr, providing a range of up to 135 miles (217 km), assuming an efficiency of 1.4 kW-hr/mile (24.6 mpg‑US (9.6 L/100 km) equivalent). The bus is charged using the SAE J1772 CCS Combo 1 connector; a full charge takes approximately 3 hours using a 60 kW DC charger.[27]

The first large order for 50 Jouley buses was placed by Dominion Energy in December 2019 as the first phase of their school bus replacement program, to be delivered by the end of 2020.[28] In February 2021, the Montgomery County Public Schools (Maryland), largest school district in the state, announced they had ordered 326 Jouley buses.[29]

Comparable productsEdit

See alsoEdit


  1. ^
  2. ^ "Archived copy". Archived from the original on April 20, 2010. Retrieved February 20, 2010.CS1 maint: archived copy as title (link)
  3. ^ a b "Company History | Thomas Built Buses". Retrieved November 15, 2018.
  4. ^ "Thomas Built Delivers 100,000th Saf-T-Liner C2 School Bus - Management - School Bus Fleet". Retrieved June 13, 2018.
  5. ^ "Thomas Built Buses Debuts First Saf-T-Liner C2 School Bus Equipped With Detroit DD5 Engine | Thomas Built Buses". Retrieved January 14, 2018.
  6. ^
  7. ^
  8. ^ "All Thomas Buses - Thomas Built Buses". Retrieved October 17, 2015.
  9. ^ "Saf-T-Liner® C2e Hybrid". Thomas Built Buses. Archived from the original on September 8, 2010.
  10. ^ "The future is now en route: C2e Hybrid" (PDF). Thomas Built Buses. July 2010. Archived from the original (PDF) on March 4, 2011.
  11. ^ Select Engineering Services (March 1, 2012). Heavy Duty Diesel Truck and Bus Hybrid Powertrain Study (PDF) (Report). U.S. Army Tank Automotive Research, Development and Engineering Center. p. 67. Retrieved March 13, 2020.
  12. ^ "Thomas tests hybrid technology on school buses" (PDF). Bus Report. Thomas Built Buses. Winter 2008. Archived from the original (PDF) on July 15, 2014.
  13. ^ "New Thomas Built hybrid shown at Arizona dealership". Schoolbus Fleet. October 1, 2009. Retrieved March 13, 2020.
  14. ^ a b MotorWeek (January 4, 2014). "Michigan Transports Students in Hybrid Electric School Buses (Text Version)". Alternative Fuels Data Center, US Department of Energy. Retrieved March 13, 2020.
  15. ^ "Thomas Built Buses Delivers Saf-T-Liner C2e Hybrid School Buses to Kentucky" (Press release). Thomas Built Buses. September 17, 2010. Retrieved March 13, 2020.
  16. ^ "New Propane-fueled Saf-T-Liner C2 in Production at Thomas Built Buses - Bus Report: May 2014 - Thomas Built Buses". Retrieved July 8, 2016.
  17. ^ "The Saf-T-Liner® C2 Propane Bus". Thomas Built Buses. Archived from the original on June 30, 2014.
  18. ^ "8.0L PIthon engine to power Thomas Built propane bus - Alternative Fuels - School Bus Fleet". Retrieved July 8, 2016.
  19. ^ "8.0 Liter Liquid Propane Gas (LPG) Engine Specification" (PDF). Powertrain Integration. August 2013. Retrieved March 13, 2020.
  20. ^ "Introducing the New DriveForce 8.8L Propane Autogas Engine" (PDF). Summer 2019. Retrieved February 26, 2021.
  21. ^ "8.8 Liter, Transportation". Power Solutions International. Retrieved February 26, 2021.
  22. ^ "Power Solutions International Announces Agreement to Purchase On-Highway Engine OEM Powertrain Integration" (Press release). Power Solutions International. May 6, 2015. Retrieved February 26, 2021.
  23. ^ "Saf-T-Liner C2 (Type C) Compressed Natural Gas (CNG) - Green Bus - Thomas Built Buses". Retrieved June 30, 2016.
  24. ^ "Thomas Built Buses (Daimler) and Proterra, the first electric school bus together". Sustainable Bus. November 15, 2018. Retrieved March 13, 2020.
  25. ^ "Daimler and Proterra, a cooperation is born. North American school bus market in the spotlight". Sustainable Bus. September 19, 2018. Retrieved March 13, 2020.
  26. ^ "Thomas Built Buses Electric School Bus Powered by Proterra® Technology Receives Full CARB and HVIP Certifications" (Press release). Thomas Built Buses. June 24, 2019. Retrieved March 13, 2020.
  27. ^ "Jouley brochure" (PDF). Thomas Built Buses. Summer 2020. Retrieved February 26, 2021.
  28. ^ Weaver, John (December 17, 2019). "Dominion chooses 50 electric Thomas Built Buses powered by Proterra". PV Magazine. Retrieved March 13, 2020.
  29. ^ Gitlin, Jonathan M. (February 26, 2021). "Maryland school district places largest-ever order for electric buses". Ars Technica. Retrieved February 26, 2021.

External linksEdit