This document outlines a rational formula for calculating gang strength using manpower norms for various maintenance activities. It categorizes activities as primary (directly related to track maintenance) or auxiliary (for overall upkeep) and further divides primary activities into routine (R) and traffic-dependent (T). Formulas are provided for calculating mandays required for different activities based on factors like traffic density, track type and condition. The document recommends works to outsource and authorities for certifying maintenance needs. It establishes manpower norms for various track configurations to replace the existing Special Committee formula.

1. GANG STRENGTH
CALCULATION USING
RATIONAL FORMULA
Presented By
K.A.J.BABU , ADEN/E/KGP,S.E.RLY
C.NAGARAJU, AXEN/C/KRMR,S.C.RLY
Under the Guidance of
Sri. PRAVEEN KUMAR,P/C,IRICEN/PUNE

2. Gang strength
 Gang strength calculation by
Maflin”s formula
Modified Maflin’s formula
Special Committee formula
Rational formulae

3. MAFLIN’S FORMULA
Adopted in 1931
No of gangmen required = Unit-per-
mile*2.5
Unit- per – mile depending on the traffic
carried
Man power factor is constant irrespective
of track gauge

4. Revised Maflin’s formula
Evolved by Lobo committee in 1959
Implemented in 1962
Gang strength was based on “Equated
Track Mile”
ETM depends on the traffic density, type
of formation, curved alignment and
annual rainfall

5. Special committee formula
Adopted in 1979
N = 0.95 * M * K * E
 N is the no of gang men
 M is man power factor ( 1.47 for B.G and 1.21 for
M.G and N.G)
 K is the correction factor due to modernisation of
track,methods of maintenance
 E is Equated Track Kilometre ( ETKM)

6. Special committee formula
 Correction factor
Type of track Mmethod of
maitenance
Convent
,DTM,M
SP
Mechanised
Fish plated 1.00 0.80
SWR 0.95 0.75
LWR on ws/ms 0.85 0.60
LWR on psc - 0.50

7. WHY SPECIAL COMMITTEE FORMULA
NEEDS REPLACEMENT
Gang is to carry out 12 activities and other 16 activities
are by engaging casual labourer
No uniformity of overall manpower per ETKM over the
railways
Maintance cost per ETKM is varying among Zonal
Railways
Decasualisation effect
Aspect of engagement of safaiwalas for filth removal

8. --Contd
Aspect of carrying out monsoon patrolling,
watching vulnerable locations and security
patrolling by out side agencies
Ageing of gang men
Absenteeism among gang men, as much as 60%
To identify the works to be executed through
contract to limit the manpower
Educational profile of the gangmen remains
deficient while mechanisation is increasingly
adopted

9. Modifying Special Committee formula
Railway Board in 1996 constituted a committee
Terms of reference
To study the special committee formula and suggest
modified formula
To take into account decasualisation done effect of
maintenance and track modernisation while modifying the
gang strenth formula

10. Categorisation of tracks
Non Sub urban sections
Machine Packed
Manually Packed
Sub urban section,Machine packed High
density

11. H D suburb section
 Criteria for High Density Sub urban Section
 The train frequency per hour, on any line or in a
sub section should exceed 8
 The required maintenance works can be
completed only by way of availing night blocks
• PHOD is the competent authority to classify a
suburban section as ‘HDSL’

12. H D suburb sections
 Special features of H D suburb section
 High frequency of trains
 Encroachments
 Corridor night blocks and integrated mega blocks
 Large number of turn outs
 Lack of drainage
 Extensive track circuits


13. CLASSIFICATION OF MAINTENANCE
ACTIVITIES
PRIMARY MAINTENCE ACTIVITIES
 Directly related to P Way maintenance
 Need manpower based on the continuous length
of the track
AUXILLIARY MAINTENANCE ACTIVITIES
 For upkeep of P Way as a whole
 Need manpower based on the localised
problems,special features and geographical nature
of P way section

14. Classification -- contd
PRIMARY MAINTENANCE ACTIVITIES
 Activity T – Affected by traffic density
 Activity R – Routine in nature
AUXILLARY MAINTENANCE ACTIVITIES
 Activity M – Miscellaneous
 Activity S – Site specific

15. Activity T ( For machine packed
track)
 T1 Slack attention to
 Bad spots
 Low joints
 SEJ
 Minor curve realignment
 T2 For Tie Tamper working
 Pre-tamping operation
 Along with tamper
 Post tamping operations
 T3 Casual renewals
 Rails
 Sleepers
 Fasteners
 T4 Repair Welding

16. Activity T ( For manually packed
track)
 T1 Through packing
 T2 Slack attention to
 Bad spots
 Low joints
 SEJ
 Minor curve realignment
 T3 Casual renewals
 Rails
 Sleepers
 Fasteners
 T4 Creep pulling

17. Activity T ( For machine packed track
HD suburban)
 T1 Slack attention to
 Bad spots
 Low joints
 SEJ
 Minor curve realignment
 T2 For Tie Tamper working
 Pre-tamping operation
 Along with tamper
 Post tamping operations
 T3 Casual renewals
 Rails
 Sleepers
 Fasteners
 T4 Repair Welding

18. Activity R ( For machine packed track)
 R1 Lubrication of ERCs
 R2 Shallow screening (1/5 length)
 R3 Loading , leading & unloading
 R4 Overhauling of level crossing
 R5 Watching caution spot and miscellaneous
 R6 Tree cutting for visibility
 R7 Lubrication of rails in Curves
 R8 Accident relief and carcass removal
 R9 Bridge sleeper attention and renewal
 R10 Pre monsoon attention such as clearing of
 drains, waterways, deweeding etc
 R11 Creep pulling (approach of bridges and turn outs)
 R12 Rectifying damage to LC

19. Activity R ( For manually
packed track)
 R1 Lubrication of ERCs
 R2 Shallow screening
 R3 Loading , leading & unloading
 R4 Overhauling of level crossing
 R5 Watching caution spot and miscellaneous
 R6 Tree cutting for visibility
 R7 Lubrication of rails in Curves
 R8 Accident relief and carcass removal
 R9 Bridge sleeper attention and renewal
 R10 Pre monsoon attention
 R11 Creep pulling
 R12 Rectifying damafe to LC

20. Activity R ( For machine packed HD
suburban track)
 R1 Through packing
 R2 Shallow screening (1/5 length)
 R3 Loading , leading & unloading
 R4 Lubrication of ERCs
 R5 Overhauling of level crossing
 R6 Watching caution spot and look out men
 R7 Tree cutting for visibility
 R8 Lubrication of rails in Curves
 R9 Accident relief and carcass removal in run over cases
 R10 Bridge sleeper attention and renewal
 R11 Pre monsoon attention
 R12 Creep pulling
 R13 Rectifying damage to LC
 R14 Painting of weld collars
 R 15 Emergency attention
 R 16 Extra sssistance to key man & B/smith
 R17 Extra work in Night blocks
 R 18 Extra assistance for S&T Items

21. Activity M
 M1 Monsoon patrolling
 M2 Hot weather patrolling
 M3 Cold weather patrolling
 M4 Watching vulnerable locations
 M5 Gate keeping at level crossings
 M6 Rest giving for keyman
 M7 Waterman duty
 M8 Store watchman duty

22. Activity S
 S1 Tunnel maintenance
 S2 Bridge substructure maintenance
 S3 Long girder maintenance
 S4 Extra due to sharp curves, deep cutting etc
 S5 Track on extremely bad formation
 S6 Lookout man duty
 S7 Fog signal man duty
 S8 Filth removal from track
 S9 Security patrolling
 S10Watching of water level in suburban section

23. Work to be done through contract
1. Formation treatment
2. Ballasting
3. Deep screening
4. Sub ballast and ballast layer
5. Heavy repair to track including lifting
6. TRR,TSR,TFR
7. Complete ROC
8. Complete renewal of P&C , SEJs , traps
9. Resurfacing of crossing and switch rails
10. Loading/unloading of P way material in bulk
11. Lorrying of P way materials in bulk
12. Security of material in depot which is closed and
locked

24. Work to be done through contract
13. Painting of rails and weld collars
14. Painting of bridge girders
15. Heavy repair to formation, cutting,side drains &c/w
drains
16. Providing and reparing road surface at LC
17. Heavy repair to bridges, protecion works,river
training works and tunnels
18. Removal of major sand breaches
19. Restoration works following breaches, accidents
20. Clearing of vegetation in P/F and in the vicinity of
tracks in coaching and goods yards, repairs to
depots and work shops of Engg, Mech, Elec and
S&T

25.  Authority for certifying the correctness of factors in
activities M & S
 No of mandays for monsoon patrolling – CTE/CBE
 Need for hot/ cold patrolling – CTE
 No.of days for watching vulnerable locations-
CTE/CBE
 Need for store w/man duty – Sr DEN/C00RD
 Existance of extremely bad formation – CTE
 Track Stretches with poor visibility – Sr DEN/Coord
 Need for fog signal duty – Sr DEN/Coord
 Need for removal of filth – Sr DEN/Coord
 Need for security patrol – Sr DEN/Coord
 No of days for watching water level in suburb-
SrDEN/Co

26. RATIONAL FORMULAE
MANPOWER
MANPOWER NORMS FOR
NORMS FOR
VARIOUS ACTIVITIES
VARIOUS ACTIVITIES

27. Rational formulae
How the manpower requirement arrived at?
Activties T & R
For Main line
 Norms as per the actual manpower utilised on
various sections on various zones and analyzing
the same scientifically
 Periodicity of shallow screening has been
changed to 5 yr instead of 3 yr
 Average spacing of the LC has been taken as 1.5
km
 Quantum of work in shallow screening in PSC
sleeper track is 4 sl / head

28. Contd
For RYL and NRYL
1 KM of NRYL is taken as equivalent to 2/3
km of RYL
Factors A,B and C are not considered
Considered as ‘R’ activity

29. MACHINE PACKED “BG”
(NON SUBURBAN)
MANDAYS REQUIREMENT/YEAR/KM.
 Activity “T” : (80 +2.3GMT)*(1+A+B+C)
 Activity “R” : 159
»“R” Modified with (+) 28 as per
Board’s letter
»+28 on a/c of overhauling 4 sleeper
instead of 6 per man for concrete
sleepers

30. Rational formulae
MANDAYS REQD. FOR ACTIVITY- T,
MACHINE PACKED
(NON- SUBURBAN) GMT-20
65
Total T1
10
As reqd.
MINOR CURVE
REALIGNMENT
4
6x8/12
6 times/yr., 8
sl/SEJ, 12 sl/head
SEJ (1 No. PER KM)
16
12x4x4/12
12 GJ/LJ 4 TIMES,
4sl/jts 12 sl/head
LOW JOINTS (FP OR
WELDED),GJ
35
1660/(4x12)
12 SL./HEAD, ¼
LENGTH
BAD SPOTS
‘T1’ SLACK ATTENTION
MD
Requirement
Norm
Activity

31. Rational formulae
MANDAYS REQD. FOR ACTIVITY- T,
MACHINE PACKED (NON-
SUBURBAN) GMT-20
10
20/2
20 men/Km
PRE-TAMPING
OPERATIONS
27
Total T2
14
28/2
28 men/Km
POST TAMING
OPERATIONS
3
10x6/(10x2)
10 men for one
week for 10 Km
gang length
ALONG WITH TAMPER
2 year cycle
T2- FOR TIE TAMPER
WORKING
MD
Requirement
Norm
Activity

32. Rational formulae
MANDAYS REQD. FOR ACTIVITY- T,
MACHINE PACKED
(NON- SUBURBAN) GMT-20
126
Total T1 + T2 + T3 + T4
12
12 men per failure/year
T4- Repair Welding
6
60/10
60 mandays /gang
length of 10 Km.
Rails
22
Total T3
10
100/10
100 mandays /gang
length of 10 Km.
Fastening
6
60/10
60 mandays /gang
length of 10 Km.
Sleepers
T3- Casual Renewal
MD
Require
ment
Norm
Activity
T= 80 + 2.3 GMT= 80 + 2.3 * 20 = 126

33. Rational formulae
MANDAYS REQD. FOR ACTIVITY- R,
MACHINE PACKED
(NON- SUBURBAN) GMT-20
4
,,
R7- Lubrication of Rails
in curves
10
,,
R6- Tree cutting for
visibility
10
Field data
R5- Watching caution
spots
13
20/1.5
1 LC/ 1.5 Km, 20 men/lc
R4- Over hauling of LC
20
Field data
R3-Loading, Leading &
unloading
55
1660/(5*6)
6 sl/head, 1/5 length
R2- Shallow Screening
2
Assistance to K-man
R1- Lubrication of ERC
MD
Require
ment
Norm
Activity

34. Rational formulae
MANDAYS REQD. FOR ACTIVITY- R,
MACHINE PACKED
(NON- SUBURBAN) GMT-20
159
TOTAL R
2
,,
R12- Rectifying damage to LC gates and
posts
5
,,
R11- Creep Pulling
18
,,
R10- Pre monsoon attention like waterway
clearance, cess repair, deweeding etc
10
,,
R9- Bridge sleeper attention and removal
10
Field
data
R8- Accident Relief- Carcass removal
MD
Require
ment
Norm
Activity

35. Rational formulae
MANUALLY PACKED “BG”
(NON SUBURBAN)
MANDAYS REQUIREMENT/YEAR/KM.
 Activity “T” : (223+8.24GMT)*(1+A+B+C)
 Activity “R” : 168
»+28 on a/c of overhauling 4
sleeper instead of 6 per man for
concrete sleepers

36. Rational formulae
MANUALLY PACKED “MG”
MANDAYS REQUIREMENT/YEAR/KM.
 Activity “T”: (160+13.56GMT)*(1+A+B+C)
 Activity “R”: 128

37. Rational formulae
MANUALLY PACKED “NG”
MANDAYS REQUIREMENT/YEAR/KM.
 Activity “T”: (105+188GMT)*(1+A+B+C)
Max. value of (105+188GMT) is 180
 Activity “R”: 91

38. Rational formulae
HIGH DENSITY SUBURBAN
MACHINE PACKED
MANDAYS REQUIREMENT/YEAR/KM.
 Activity “T” : (115 +2.3GMT)*(1+A+B+C)
 Activity “R” : 398

39. Rational formulae
RUNNING YARD LINE(RYL) and
NON RUNNING YARD LINE(NRYL)
RLY mandays are 74 % to 79% of R & T activities for
mainline with “0” GMT
NRYL mandays are 2/3rd of RLY mandays
Factors A, B, C not to be applied
*This includes equivalent MMU mandays
102
152
198
-
NRYL
153
228
297
177*
RYL
NG
Manually
packed
MG
Manually
packed
Manually
packed
Machine
packed
BG

40. MANDAYS REQUIREMENT FOR ACTIVITY
“M”
M.1 Monsoon
Patrolling
N: Total No. of beat-lengths
D: No.of days needing patrolling
in a year in the nth beat length.
b: No.of beats in the nth beat
length.
s: No. of shifts in the nth beat
length
m: No.of men in each shift in the
nth beat-length =2 in area
infested with wild animals/
terrorists; otherwise m=1.
1 to N
 
m
s
b
D 




41. MANDAYS REQUIREMENT FOR ACTIVITY
“M”
M.2 Hot weather
patrolling of
LWR track
Lw X 30
M.3 Cold weather
patrolling of
LWR track
Lw X 12
Lw: Length of LWR track in
km, on single line basis

42. MANDAYS REQUIREMENT FOR ACTIVITY
“M”
M.4 Watching
vulnerable
locations
1 to N
M.5 Gate keeping
at level
crossings
1 to N
N: No. of vulnerable locations
s: No.of duty shifts at the nth
location
d:No.of days of watching at the
nth location in a year.
N: No. of Engg level crossings
s: No.of duty shifts at the nth
level crossing
Ng: No. of Engg Gatekeeper
posts sanctioned
(Excluding LR)
 
d
s 

Ng
s 294
*
365 


43. MANDAYS REQUIREMENT FOR ACTIVITY
“M”
M.6 Rest giving
for keymen
K(365-294)
M.7 Waterman
duty
N * 294
M.8 Store-
watchman
duty
N * 3 * 365
K: No. of Keyman beats
N: No. of Gangs
N: No. of stores in addition to
SSE HQ (Not more than 2)

44. MANDAYS REQUIREMENT FOR ACTIVITY
“S”
S.1 Tunnel
Maintenance
1.2* 0.29*
1 to N
S.2 Bridge
substructure
maintenance
1.1* 0.29*
1 to N
N: No. of tunnels
l: length of the nth
tunnel, in metre
r: No.of tracks in the
nth tunnel.
N: No.of bridges
b: Lineal waterway of the nth
bridge, in metre
r: No. of tracks on the nth bridge.
 
r
l 

 
r
b 


45. MANDAYS REQUIREMENT FOR ACTIVITY
“S”
S.3 Long Girder
Maintenance
0.64*
1 to N
S.4 Sharp curves
> 3 D in BG
> 6 D in MG
Lc * 294
N: No. of bridges each having
more than 150m lineal
waterway
b: Lineal waterway of the nth
bridge, in metre
r: No. of tracks on the
nth bridge
Lc: Total Length of such curve
 
r
b 


46. MANDAYS REQUIREMENT FOR ACTIVITY
“S”
S.5 Track
maintenance
in extremely
bad formation
0.6 *
1 to N
S.6 look out man
294
1 to N
N: No.of locations where
track needs more than
4 attentions in a year
l: length of track in the nth
location, in metres
N: No. of gangs
v: length of track with poor
visibility in the nth gang length
g: length of the nth gang
 
g
v /

 
l


47. MANDAYS REQUIREMENT FOR ACTIVITY
“S”
S.7 Fog signalman
Mf / 3
S.8 Filth removal
from track
f * 294
S.9 Security
Patrolling
Ms / 3
Mf: Total Mandays actually utilised
in past three years
f: No. of gangs having this kind of
problem
Ms: Total Mandays actually
utilised in past three years

48. MANDAYS REQUIREMENT FOR ACTIVITY
“S”
S.10 Watching
water level in
suburban
sections
1 to N
N: No.of locations where flooding
of track occurs in rainy season,
due to water entering from
built-up area outside.
s:No.of shifts required at the nth
location.
d:No. of days requiring watching
at the nth location. Normally s =
2; d= 60 in Mumbai suburban
sections.
 
d
s 


49. MANDAYS REQUIREMENT FOR ACTIVITY
“S”
S.10 Watching
water level in
suburban
sections
1 to N
N: No.of locations where flooding
of track occurs in rainy season,
due to water entering from
built-up area outside.
s:No.of shifts required at the nth
location.
d:No. of days requiring watching
at the nth location. Normally s =
2; d= 60 in Mumbai suburban
sections.
 
d
s 


50. EQUIVALENT LENGTH OF
SPECIAL LAYOUTS
a) Same as per SPECIAL COMMITTEE FORMULA
Turnout 0.1 Km
Diamond 0.1 Km
Diamond crossing with single slip 0.15 Km
Diamond crossing with double slips 0.2 Km
Cross over 0.2 Km
Three-throw 0.2 Km
Scissors cross-over 0.5 Km
Trap 0.02 Km
Double trap 0.04 Km

51. MULTIPLYING FACTORS
Factor As per Special
Committee
As per MCNTM
A 0.1 and 0.2 for bad and
very bad formations
Same
B =0.25 for > 1.5 D for BG
> 3 D for MG
> 5 D for NG
Linear from 0 to 0.25 for
1 to 2 D for BG,
2 to 4 D for MG
3 to 7 D for NG
thereafter constant at 0.25
C =0 up to rainfall of 200 cm
=0.1 for rainfall of 200 cm
=Linear from 01 to 0.2 for
rainfall 200 to 300cm
=0.2 for rainfall > 300 cm
=0 up to rainfall of 150 cm
= Linear from 0 to 0.2 for
rainfall 150 to 300cm
=0.2 for rainfall > 300 cm

52. SUMMARY
TYPE MANDAYS/KM ACTIVITY
“T”
MD/KM
ATY “R”
MAC. PACKED BG
(NON- SUB URBAN)
(80+2.3*GMT)X(1+A+B+C) 159
MAN. PACKED BG
(NON SUB URBAN)
(223+8.24*GMT)X(1+A+B+C) 168
MAC. PACKED BG
(HD - SUB URBAN)
(115+2.3*GMT)X(1+A+B+C) 398
MAN. PACKED MG (160+13.56*GMT)X(1+A+B+C) 128
MAN. PACKED NG (105+188*GMT)X(1+A+B+C) 91

53. SUMMARY
TYPE MANDAYS/KM ACTIVITY
“T”
MD/KM
ATY “R”
MAC. PACKED BG
(NON- SUB URBAN)
(80+2.3*GMT)X(1+A+B+C) 159
MAN. PACKED BG
(NON SUB URBAN)
(223+8.24*GMT)X(1+A+B+C) 168
MAC. PACKED BG
(HD - SUB URBAN)
(115+2.3*GMT)X(1+A+B+C) 398
MAN. PACKED MG (160+13.56*GMT)X(1+A+B+C) 128
MAN. PACKED NG (105+188*GMT)X(1+A+B+C) 91

54. SUMMARY
TYPE MANDAYS/KM ACTIVITY
“T”
MD/KM
ATY “R”
MAC. PACKED BG
(NON- SUB URBAN)
(80+2.3*GMT)X(1+A+B+C) 159
MAN. PACKED BG
(NON SUB URBAN)
(223+8.24*GMT)X(1+A+B+C) 168
MAC. PACKED BG
(HD - SUB URBAN)
(115+2.3*GMT)X(1+A+B+C) 398
MAN. PACKED MG (160+13.56*GMT)X(1+A+B+C) 128
MAN. PACKED NG (105+188*GMT)X(1+A+B+C) 91

55. SUMMARY
 Staff strength arrived at by rational formulae
does not include
– LR of 12.5 %
– Posts of Gateman, Mates, Keymen, Artisans, Artisan
helpers, Trollyman, Storeman
– USFD team
– Machine Staff for maintenance or operation
 Report recommended 2% training reserve, Board yet
to take final view

56. MMU STAFF
 Work load catered by MMU (Machine Packed only)
Main Line Activity
T= 80 + 2.3* GMT
For GMT of 20,
T=126
Bad spots 35 out of 35
Low joints 10 out of 16
SEJ 2 out of 4
Curves 6 out of 10
Casual renewal rail 2 out of 6
Casual sleeper rail 2 out of 6
Repair welding 6 out of 12
63 I.e 50%
40+1.15
GMT
Main Line activity
R= 159
Loading Unloading 12 out of 20
OH of LC 13 out of 13
Bridge sleeper renewal 7 out of
10
Creep pulling 3 out of 5
35

57. MMU STAFF
 Work load catered by MMU (Machine Packed only)
Running Yard Line
R=177
Bad spots 14 out of 14
Low joints 5 out of 8
Curves 2 out of 6
Casual renewal rail 2 out of 3
Casual sleeper renewal 2 out of 3
Loading Unloading 10 out of 15
35
Gross Equivalent MMU
Mandays i.e GEMM
= Lm(40+1.15 GMT) (1+A+B+C)
+ 35 Lm + 35 Ly
Exp. on MMU 80 % of Emoluments of GEMM=
Annualized cost of SEMMU + Annual
emoluments of MMU staff




58. CONCEPT OF EMKM
 Committee has proposed Equated Manpower
KM (EMKM) as performance unit in place of
ETKM
 EMKM is defined as numerical equivalent to
0.6 times the number of gang man required
for activities T, R, M, S
– EMKM has been defined based on a
compensator p-way section requiring 1.66
men/KM

59. RATIONAL FORMULAE
How these are different ?
Zero based approach has been adopted
Formulae have been evolved on rational basis
14 non – suburban sections and 3 HD suburban sections
have been studied on 7 Zonal Railways (
NR,ER,WR,SR,CR,SER,SCR) through direct interaction
with the field Engineers

60. Rational formulae
What is new ?
Mandays per annum per km for each activity are computed instead
of man power factor
Man power requirement for T & R activities is same irrespective of
the type of sleepers and type of rails i.e., F.P,SWR,LWR
All the sub activities of maintenance of RYL and NRYL are
categorised under activity R (Routine maintenance )
Flexible to encourage formation of Mobile Maintenance Units (
MMUs)
Concept of Equated Manpower Kilometre (EMKM) introduced
EMKM = 0.6 ( G/men per km as per Rational formulae )

61. Rational formula
 Conclusions
1. As the formulae are arrived at more rationally, there will be saving in the
manpower and at the same time ensures equitable distribution of
manpower in accordance with the work load.
2. The adoption of rational formulae ensures uniformity of manpower
provision commensurate with work load.
3. Optimisation of manpower can be achieved
4. uniform degree of track maintenance and equitable allotment of funds.
5. The concept of EMKM enables to evaluate the manpower requirement
for optimal utilization
6. The formulae are more flexible to allow for redistribution of strength of
the various gangs as per the age profile of track.
7. The formulae allows for introduction of Mobile Maintenance Units