Union Pacific Railroad
Roster of Road Slug Units
This page was last updated on August 24, 2014.
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Road Slug Model S4-B -- 1 unit
B-B trucks; 249,000 pounds operating weight
Road Number |
First Number |
Rebuild Date |
Rebuilt From |
Date To S50 |
New Number |
Date To New Number |
UP S50 | MKT 501 | Jul 1982 | MKT GP40 222 | 20 Mar 1989 | S300 | 1 Feb 1991 |
General Notes:
- Built as MKT road slug 501 from wrecked MKT GP40 222; renumbered and repainted to UP S50 on 20 March 1989, at the same time as matching GP40 slug control units, UP 595 and 596 (ex MKT 226, 227).
- Operated with UP 3000 and 3001, former MKT GP40s.
Road Slug Model S4-B -- 1 unit
B-B trucks; 249,000 pounds operating weight
Road Number |
First Number |
Second Number |
Rebuild Date |
Rebuilt From |
Date To S50 |
Date To S300 |
Date To UPY 926 |
UP S300 | MKT 501 | UP S50 | Jul 1982 | MKT GP40 222 | 20 Mar 1989 | 1 Feb 1991 | 17 Dec 2003 |
General Notes:
- Built as MKT road slug 501 from wrecked MKT GP40 222; renumbered and repainted to UP S50 on 20 March 1989, at the same time as matching GP40 slug control units, UP 595 and 596 (ex MKT 226, 227).
- Operated with UP 3000 and 3001, former MKT GP40s.
- Model was changed from SL-1 to S4-B on 14 April 1992; changed from freight service to switching service on same date.
- Renumbered to UPY 926.
Road Slug Model S5-2B -- 3 units
B-B trucks; 256,000 pounds operating weight
Road Number |
Rebuild Date |
Rebuilt From |
UPY Number |
Date To UPY Number |
UP S301 | 5 Apr 1991 | KCS GP30 4104 | UPY 927 | 30 Apr 2001 |
UP S302 | 5 Apr 1991 | KCS GP30 4108 | UPY 928 | 29 Mar 2001 |
UP S303 | 5 Apr 1991 | KCS GP30 4119 | UPY 929 | 19 Feb 2002 |
General Notes:
- Rebuilt from retired KCS GP30s by Morrison Knudsen, Boise, Idaho.
- Equipped with 2,600 gallon fuel tanks, and pumping equipment to transfer fuel between slug and attached slug control units; sensing monitors activate the pumps to keep fuel level equalized between the control units and the slug.
- All three road slugs operate with UP GP40-2 slug control units.
- Renumbered to UPY 927-929.
Road Slug Model S3-3BDE -- 1 unit
B-B trucks; 280,000 pounds operating weight
Road Number |
First Number |
Rebuild Date |
Rebuilt From |
Date Retired |
(UP S310) | SP 1600 | 1 May 1980 | UP U25B 634 | 25 Jul 2000 |
General Notes:
- One unit to UP at merger, numbered SP 1600.
- SP 1600 built by Morrison-Knudsen from UP U25B 634 (retired by UP in September 1972, sold to MK in August 1974) as a prototype for SP's own planned road slug program; the MK rebuilding included new step wells and a new low carbody, with new sand boxes and extra ballast.
- Equipped with 2900-gallon fuel tank and pumping equipment to transfer fuel from the slug and the attached control units; sensing monitors activate the pumps to keep the fuel level equalized between the control units and the road slug.
- Former SP designation was TEBU (Tractive Effort Booster Unit).
- Equipped to operate with former SP 7940-7959 group GP40-2s (built in April and May 1980) and former SSW 7960-7966 group GP40s (rebuilt in 1981 and 1982).
- Stored by UP at North Platte, Nebraska, during late 1998.
- Assigned UPY 930, not renumbered prior to being retired.
Road Slug Model S3-2B -- 10 units
B-B trucks; 280,000 pounds operating weight
Road Number |
First Number |
Rebuild Date |
Rebuilt From |
Date To UP Number |
UPY Number |
Date To UPY Number |
Date Retired |
Notes |
(UP S311) | SP 1601 | 1 May 1981 | SP U25B 6761 | 25 Jul 2000 | ||||
(UP S312) | SP 1602 | 29 May 1981 | SP U25B 6765 | 26 Mar 1997 | 1 | |||
UP S313 | SP 1605 | Aug 1981 | SP U25B 6747 | 19 Jan 1998 | UPY 932 | 14 Jan 2004 | ||
(UP S314) | SP 1606 | Sep 1981 | SP U25B 6712 | 28 Dec 1999 | ||||
(UP S315) | SP 1608 | Nov 1981 | SP U25B 6711 | 25 Jul 2000 | ||||
(UP S316) | SP 1609 | Dec 1981 | SP U25B 6713 | 25 Jul 2000 | ||||
(UP S317) | SP 1610 | Jan 1982 | SP U25B 6751 | 26 Mar 1997 | 2 | |||
UP S318 | SP 1611 | Mar 1982 | SP U25B 6754 | 27 Jul 1999 | UPY 936 | 14 Jan 2004 | ||
UP S319 | SP 1612 | May 1982 | SP U25B 6758 | 18 Sep 1997 | UPY 937 | 29 Aug 2003 | ||
(UP S320) | SP 1613 | Jun 1982 | SP U25B 6766 | 25 Jul 2000 |
General Notes:
- Original total of 13 units; 10 units went to UP at merger; SP retired three units (SP 1603, 1604, and 1607) prior to the merger.
- SP's road slugs were rebuilt by its Sacramento shops from the road's own retired U25Bs.
- Equipped with 2900 gallon fuel tank and pumping equipment to transfer fuel from the slug and the attached control units; sensing monitors activate the pumps to keep the fuel level equalized between the control units and the road slug.
- Former SP designation was TEBU (Tractive Effort Booster Unit).
- Equipped to operate with former SP 7940-7959 group GP40-2s (built in April and May 1980) and former SSW 7960-7966 group GP40s (rebuilt in 1981 and 1982).
- SP 1601, 1608, 1609, 1613 stored by UP at North Platte, Nebraska, during late 1998.
- UP S319 (ex SP 1612) was the first of this group to be repainted to Union Pacific, completed on 18 September 1997.
- Renumbered to UPY 931-938.
Notes:
- SP 1602 was sold to National Railway Equipment on 28 April 1977.
- SP 1610 was sold for scrap to Louisville Scrap, 28 February 1998.
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