OPTIMISING THE SPEED POTENTIAL OF CURVES: INCREASE IN PERMISSIBLE

CANT DEFFICIENCY- FEASIBILITY AND CHALLENGES

- S.K. Pandey, Ex. Director/Track, RDSO

- Ajay Kumar, Director/Track, RDSO*

- * Presenter of paper

SYNOPSIS

Indian Railways has approximately 16% of Broad Gauge track on curves. Due to mixed traffic

conditions, maximum value of cant is restricted on account of design considerations and operational

speed of freight vehicles. This restriction puts a cap on maximum permissible speed for passenger

vehicles and locomotives. For realizing the full benefit of semi high speed operation (speeds up to 160 –

200 km/h) on existing track, it would be imperative to optimize speed on curves simultaneously. The

speed potential of curves can be increased by permitting higher cant deficiency but the associated

issues with respect to vehicle and track design and maintenance need to be addressed. Increase in the

cant deficiency value from existing 75 mm to 100 mm will increase the speed potential of curves by 6-

8% and will result in removal of sizeable number of speed restrictions. This paper makes an attempt to

evaluate the status on IR and suggests ways ahead to explore the possibilities of permitting higher cant

deficiency for increasing speed over curves and challenges likely to be encountered in the way of

finding a low cost solution.

1.0 INTRODUCTION

1.1 The vehicles while negotiating a curve is subjected to centrifugal force, which apart from

causing discomfort to passengers may lead to unsafe operating conditions by way of

excessive lateral force or tendency of overturning of vehicle at high speeds. The

magnitude of centrifugal force is primarily dependent upon curvature and speed of

operation. This centrifugal force is mitigated by providing cant, the value of which depends

on the curvature and speed of vehicle. There will be an equilibrium value of cant for a

particular speed for a given degree of curve that will completely mitigate the centrifugal

force. A vehicle running at a speed, higher than the equilibrium speed, will run in a regime

of cant deficiency, while the vehicle running at speed less than equilibrium speed will

cause cant excess. The cant excess leads to increased loading on inner rail resulting into

increased rate of wear of rails and increased maintenance effort. The ideal situation for

track would be that vehicle negotiates a curve with zero cant deficiency or cant excess i.e.

the track is laid with equilibrium cant. This is not practically feasible in mixed traffic

scenario where there is differential speed between passenger and freight trains. The

Indian Railways is a mixed traffic regime, where passenger trains are running at a speed

of 110-130 kmph and freight trains are running normally at 75 kmph. Therefore, a balance

is to be struck in between maximum cant, maximum cant deficiency and maximum cant

excess to provide safe, stable and comfortable operation at all permissible speeds of

different rolling stocks along with least operation and maintenance cost.

1.2 On curved track of a given curvature, a vehicle running at speed higher than equilibrium

speed will experience the cant deficiency which will depend on the speed. As a result of

the cant deficiency, there is spring deflection, leading to on-loading on the outer rail and

off-loading on the inner rail. Similarly, there will be lateral forces on the outer rail and also

steady lateral accelerations in the vehicle. These changes in the vertical loadings, lateral

forces and lateral accelerations exist even on a uniformly curved track without any local

defects. Increasing speeds through curves will increase the lateral force exerted on track

during curving, thus requiring more intensive track maintenance to maintain safety.

1.3 Thus, on existing routes, the speed of operations can be increased to some extent by

permitting higher cant deficiency, duly considering the factors involved in design and

maintenance of Track and Rolling stock.

2.0 FACTORS GOVERNING CANT AND CANT DEFICIENCY

2.1 Maximum Permissible Cant:

.1 In case of mixed traffic regime, the maximum value of cant to be decided considering the following

factors:

- Passenger discomfort in slow moving train

- Risk of derailment for freight trains due to uneven loading on the rails.

- Possible shifting of freight load.

- Possible breakaway (parting) of freight train from standstill because of high level of friction

of wheels against the inner rail.

- Permitted C.G. values of rail cars

The above mentioned problems can be aggravated by high cross winds. Large cant can also result in

lateral displacement of track towards the centre of curves during tamping at low temperature. A smaller

cant is therefore preferable but will require higher cant deficiency at higher speeds.

.2 For these reasons, some limit of maximum cant in curves is to be set. For Broad Gauge of Indian

Railway maximum permissible value of cant has been set as:

- 165 mm for A, B & C routes (Routes having higher speed potential in excess of 110 kmph

and suburban routes)

- 140 mm for D & E routes ( Other Routes)

2.2 Maximum Permissible Cant Deficiency:

.1 The Cant deficiency causes flanging on higher rail thus increased lateral wear of rail head. The

uncompensated lateral acceleration caused due to cant deficiency also gives riding discomfort.

.2 The uncompensated lateral acceleration due to cant deficiency can be worked out as under :

ad = (g /G) x Cd Cd = cant deficiency considering g = 9.81 m/s

2

and G= 1750 mm (Dynamic gauge for Broad Gauge Track)

ad = Cd/ 178.4 m/s

2 ---- (I)

The uncompensated lateral acceleration causes lateral force proportional to axle load. Considering 20T

axle load and 1m/s² of lateral acceleration, this lateral force will be 20KN. This lateral force will be

supplemented by LWR force and by dynamic load, which depends on track and vehicle maintenance.

.3 Practical limits for cant deficiency should, therefore, be set taking following factors into

consideration:(4)

a) Track construction

b) State of track components

c) Track geometry

d) Type of Bogie

e) Axle load and unsprung mass

f) Maintenance conditions of vehicle.

To allow high value of cant deficiency, track component must be designed for that. In addition, lateral

track resistance immediately after tamping should not be exceeded. Increase in cant deficiency leads

to faster deterioration of track also.

.4 Effect of suspension on lateral acceleration: (4)

The centrifugal force due to lateral acceleration exerted at centre of gravity of vehicle will cause an

overturning moment due to which spring system of vehicle will be compressed. This will cancel out

some cant virtually leading to increased cant deficiency hence lateral acceleration by a factor k, called

suspension factor.

Aeq = ( 1 + k ) ad

Aeq should preferably be below 1m/sec2

and in no case should exceed 1.5 m/sec2.

Considering a

suspension factor of 0.4 for modern rolling stocks, the Aeq will be 1.4 ad and based on the equation (I)

given above, the maximum theoretical value of Cd for Broad Gauge can be 127 mm for

unbalanced lateral acceleration of 1 m/s2

and 190 mm for unbalanced lateral acceleration of 1.5

m/s2.

.5 For Broad Gauge of Indian Railway maximum permissible value of cant deficiency has been set as:(6)

- 100 mm for speeds in excess of 100 kmph on Group A & B routes for nominated rolling

stock and routes.

- 75 mm for routes not covered above.

3.0 STUDIES CONDUCTED FOR JUDGING EFFECT OF HIGHER CANT DEFIFIENCY ON INDIAN

RAILWAYS

3.1 The studies have been conducted by RDSO to assess the effect of increasing cant deficiency on rail

stresses, lateral loads, stability against rail climbing and lateral and vertical riding behavior of various

rolling stocks. The results have been indicated in different reports. The observations of three studies are

being discussed as follows.

3.2 Studies for increasing the speed on Delhi – Howarah route (1)

3.2.1 The study was conducted with primary consideration that the increase of speeds proposed

should be achieved without any large scale additional expenditure. As such, it is necessary that

increase of speeds should be only to the extent as would be possible without involving any large

scale realignment of curves. Thus, the existing curvature and transition lengths would have to be

retained and the possibility of increasing the permissible speeds on the curves was investigated on

the basis that a somewhat better and more uniform standard of maintenance could be achieved for

curves and transitions on high speed track. The analysis of the data, in the case of curves was

made with a view to determining;

(a) The extent of cant deficiency which could be permitted for the operation of the WDM4

locomotive and ICF all coil coach at higher speeds.

(b) The speeds which could be permitted on transitions to the present standard, i.e. with a cant

gradient of 1 in 720.

(c) The limiting values for track defects which could be permitted on the curves and the transitions.

3.2.2 The safety, stability and the general ‘riding comfort of the vehicles were judged by assessing

the vertical load variations, lateral forces, vertical accelerations and lateral accelerations, as

measured in the vehicles.

3.2.3 Based on studies, charts were prepared, to indicate the relationship between the following:

(a) Cant deficiency and off-loading (at spring level) for WDM4 locomotive.

(b) Cant deficiency and on-loading (at spring level) for WDM4 locomotive.

(c) Cant deficiency and off-loading (at spring level) for ICF coach.

(d) Cant deficiency and on-loading (at spring level) for ICF coach.

(e) Cant deficiency and lateral force (at axle level) for the WDM4 locomotive on:

Curves with radii in the range of 700 to 800m.

Curves with radii in the range of 900 to 1400 m.

(f) Cant deficiency and lateral acceleration in the WDM4 locomotive.

(g) Cant deficiency and lateral acceleration in the ICF coach.

3.2.4 The off-loading and on-loading at spring level and rail level for the WDM4 locomotive as

recorded is as under:

Cant deficiency

(mm)

Calculated value (tonnes) of off-loading at

Calculated values (tonnes) of on-loading at

Spring Level Rail Level Spring Level Rail Level

100 0.51 1.10 0.58 1.19

125 0.64 1.35 0.72 1.45

150 0.74 1.58 0.85 1.71

The off-loading for a cant deficiency of even 150mm are only 1.58 tonnes and 0.74 tonnes at rail

level and spring level respectively. The values are appreciably smaller for a cant deficiency of

100mm. The values of ‘off-loading’ and ‘on-loading’ referred above are only the ‘steady’ values on

account of the cant deficiency.

3.2.5 The off-loading and on-loading at spring level and rail level for the ICF Coach, as recorded is as

under:

Cant deficiency

(mm)

Calculated value (tonnes) of off-loading at

Calculated values (tonnes) of on-loading at

Spring Level Rail Level Spring Level Rail Level

100 0.35 0.53 0.39 0.57

125 0.43 0.65 0.48 0.72

150 0.50 0.77 0.56 0.86

It is seen that the off-loading and on-loading on account of cant deficiency is small for a cant

deficiency of even 150mm.

3.2.6 The values of lateral forces, as measured at axle box level of the WDM4 locomotive are given in

the table below:

Cant deficiency

(mm)

Observed values of lateral forces (tonnes)

Curve No. 1 and 4 radius 900 to 1400m

Curve No. 2 and 3 radius 700 to 800m

Axle 4 Axle 6 Axle 4 Axle 6

100 1.08 0.00 0.50 0.46

125 1.28 0.00 0.65 0.57

150 1.48 0.00 0.79 0.68

It is seen that the lateral forces on account of cant deficiency are comparatively small. It is

interesting to note that the lateral forces are somewhat larger in the flat curves No.1 and 4 as

against the sharp curves No.2 and 3. The reason for this is that on the flat curve, no lateral forces

were recorded on axle no.6, the lateral force carried by axle no.4 being correspondingly more. In

the sharper curves, the lateral forces are shared by the two axles.

3.2.7 The lateral accelerations on account of cant deficiency, in the WDM4 locomotive are extracted

in the table below:

Cant deficiency Lateral acceleration (calculated)

(mm) (g)

100 0.072

125 0.085

150 0.105

3.2.8 The lateral accelerations on account of cant deficiency for the ICF coach, are extracted in the

table below:

Cant deficiency Lateral acceleration (calculated)

(mm) (g)

100 0.069

125 0.085

150 0.101

The values for the locomotive and the coach are practically the same and the magnitude of

accelerations for a cant deficiency of 100mm are small, when compared to the permissible limiting

figures of 0.3/0.35g, for local peak acceleration values.

3.2.9 From the data presented above, it would be observed that a cant deficiency of the order of

100mm does not result in any large values of wheel off-loading and on-loading, lateral forces or

lateral accelerations. Thus, the extent of cant deficiency to be permitted in India, for an operating

speed of 120/125 kmph, is to depend on the standards which could be achieved in the

maintenance of the track of curves. Considering the practical difficulties in achieving a uniformly

very high standard of track maintenance for higher speed operation, it was recommended that the

maximum permissible cant deficiency for higher speed operation be fixed at 100mm.

3.3 Studies to assess effect of Cant Deficiency on distribution of lateral and vertical forces : (2)

3.3.1 The studies were conducted with WDM4 loco on a 2° curve up to speed of 120 kmph

simulating cant deficiency up to 145 mm. The track studies were meant for studying the effect of

increased cant deficiency on various track components. The combined track vehicle studies were

meant for studying whether a correlation can be established between track and vehicle

parameters.

3.3.2 Observations made during study :

(i) Nominal wheel load = 9.4 T

(ii) Maximum dynamic wheel load assessed = 15.19 T (61.5% higher than

nominal)

(iii)Maximum Bogie load observed = 73.47 T (30.2% higher than nominal)

(iv)Maximum value of lateral force Y = 4.80 T

(v) Maximum Y/Q = 0.41

(vi)Ratio of horizontal axle thrust H and axle load P at track level

(Max. H/P ratio) = 0.25

3.3.3 Summary of the results :

1. Correlation between cant deficiency and lateral forces (Y) at track level:

- It was observed that total Y forces do not differ very much from speed to speed. As such a

present limit of 100mm cant deficiency on a 2° curve can even be considered for increase

to some suitable higher value after conducting more trials.

2. Correlation between cant deficiency and vertical wheel load:

- No correlation could be drawn due to want of sufficient data.

3. Correlation between cant deficiency and H forces measured at axle box level:

- No substantial increase is noticed in H/P ratio with increase in speed.

4. Correlation between cant deficiency and lateral and vertical accelerations observed at loco

floor:

- No correlation could be established.

- Maximum value of lateral acceleration observed was 0.18g at 90kmph as well as at

120kmph.

- Maximum vertical acceleration observed was 0.20g at 120kmph.

5. Rail Stress:

5.1 Maximum value of vertical bending stress at rail foot observed as

Speed (km/h) 90 100 110 120

Stress (Kg/mm2) 12.12 10.7 11.1 9.6

(inner rail) (inner rail) (outer rail) (Outer rail)

5.2 Maximum stress in rail flange was observed at 14.25 Kg/mm

2 at speed of

90kmph.

Above values are within the fatigue limit of rail steel.

5.3 Maximum stress at rail head on the outer face has been observed as 11.2 Kg/mm2 on the

inner rail at 120kmph. The maximum calculated head stress on the inner face for outer rail

is 19.6 Kg/mm2 at 120kmph.

6. Dynamic Wheel Load:

6.1 The theoretical mean load transfer was found to vary with

- Speed

- rolling stock

- measuring location

The theoretical mean load transfer as due to cant effect and the actual mean load transfer

as observed differed to quite a good extent, the amount of disparity increasing with

increasing speed indicating that the rolling motion of vehicle and defects in track may be

responsible to quite a good extent in load transfer in addition to cant effect.

6.2 The maximum dynamic wheel load observed was 15.9T which was 61.5% higher than

nominal wheel load.

7. Lateral Forces:

7.1 Maximum value of lateral force observed at different speeds was as under:

Speed (Km/h) 90 100 110 120

Lateral Force (T) 3.55 3.6 3.75 4.8

7.2 Maximum value of Y/Q ratio observed as 0.41

7.3 Maximum value of H/P ratio was observed to be 0.25.

8. Correlation between cant deficiency and track and vehicle parameters:

8.1 A good correlation could be found out between the speed (cant deficiency) and H forces

measured at the axle 4 of the WDM4 diesel-electric locomotive. An extrapolation of the

relation up to 160 km/h (strictly not permissible) yielded satisfactory H/P values at 160

km/h well within the track distortion criteria. This gives a possibility of making such similar

detailed studies to get at a possible correlation and this may be feasible in view of the H

values observed at the axle box of vehicle being without much scatter.

8.2 A good correlation could be found out between the speed (cant deficiency) and Y forces

measured at outer wheel of axle 2 and inner wheel of axle 4. It has been observed that the

(curving + dynamic) components of Y reduce with increase of speeds from 90 to 120 km/h.

When the corresponding cant deficiency effects at various speeds are added to the above

values of the curving and dynamic effects, the total Y force does not vary much in the

speed range 90 to 120 km/h. This shows that Y forces do not vary much with increased

speeds.

9. Conclusions:

It has been found that WDM4 diesel-electric locomotive behave very satisfactorily up to a

speed of 120 km/h on two degree curve. The various stresses on the track, the derailment

and track distortion coefficients have remained within the acceptable limits. The study of the

effect of increased cant deficiency on the transverse forces in the track and H forces in the

vehicle has indicated the following:

(i) The Y forces remain without much difference with increased cant deficiency up to

145mm.

(ii) The H forces increase with increase in cant deficiency upto 145mm. But the value of H

remains within the permissible limit as indicated by the H/P ratio.

(iii) The extrapolation of the Y and H forces even up to a higher cant deficiency figure

corresponding to 160km/h speed (strictly extrapolation is not permitted) indicate the same

trend (i) and (ii) above. Further trials should be conducted to study this aspect in greater

details.

3.4 Further studies to assess effect of Cant Deficiency on distribution of lateral and vertical

forces : (3)

3.4.1 These studies were conducted in continuation to those undertaken earlier (Para 3.3 above)

to assess the effect of Cant Deficiency on distribution of lateral and vertical forces on the inner

and outer rails of a curve. Studies were conducted with WDM2 Loco up to speed of 120kmph on

20 curve simulating cant deficiency up to 145mm.

3.4.2 Observations :

1. The maximum axle load observed was 27.4T and the assessed value was 28.4T.

2. The maximum value of Y/Q ratio was 0.54 at 120 kmph.

3. The maximum value of H/P ratio was 0.33 at 120 kmph.

3.4.3 Summary & Conclusions:

1. Dynamic wheel load : The mean wheel load increases on outer rail and decreases on

inner rail with increase in speed. The assessed maximum value of wheel load was

16.3 T at 120 kmph.

2. Lateral forces: The lateral forces increases on outer rail with increase in speed. The

maximum observed lateral force was 6.1t at 120 kmph whereas maximum assessed

value was 6.3t.

3. Rail Flange Stress: The maximum value of rail flange stress was 14.4 Kg/mm² on outer

rail at 110 kmph. This value is within safe limit of rail steel.

4. Correlation between cant deficiency and track and vehicle parameters: No good

correlation could be obtained between cant deficiency and Y forces measured at outer

and inner wheel of axle 6.

5. Satisfactory correlation could not be obtained between speed and axle load and wheel

load.

4.0 EFFECT OF HIGHER CANT DEFICIENCY ON ROLLING STOCK:

4.1 In order to negotiate higher cant deficiency, vehicle maintenance standards and certain vehicular

design features such as type of bogie, axle load and unsprung mass etc. are important. Some criteria

have been set worldwide to qualify vehicles for negotiating higher cant deficiency. The salient ones are

being discussed here.

4.2 Stipulations of AREMA Manual: (7)

1. Centrifugal force at curves is balanced by component of body weight perpendicular to track

plane.

2. The car body assumes a different position when speed of car is greater than equilibrium speed.

With the unbalanced centrifugal force acting at C.G. of car body, the body will be displaced

outwardly and will tilt on the springs.

3. Under normal conditions when the car is above the equilibrium speed, the car body will not

incline from vertical at an angle as great as the track angle. The difference between the track

angle and car angle is called the roll angle. The less the roll angle, the better comfort obtained

in going around curve.

4. Safety and comfort limit the speed with which a car can negotiate a curve. Any speed which

gives comfortable riding is well within the limits of safety also. Experience has shown that

passenger coaches will ride comfortably around a curve at speed which will require an elevation

about 3 inches higher for equilibrium.

5. Equipments designed with large centre bearings, roll stabilizers and outboard swing hangers

can comfortably negotiate curves at greater than 3 inches unbalanced elevation because of

less car body roll. It is suggested that for such coaches a “lean test” be made on the coach to

ascertain car body roll. If the roll angle is less than 1030’, experiments indicate that car can

negotiate curves comfortably at 4 ½ inches unbalanced elevation.

4.3 FRA stipulations for vehicles to operate at cant deficiency in excess of 3 inch:

(10)

Each vehicle type must be approved to operate on track with a qualified cant deficiency, greater than 3 inches. Each vehicle type must demonstrate, in a ready-for-service load condition, compliance with the requirements of either paragraph (1) or (2) mentioned below.

(1) When positioned on a track with a uniform superelevation equal to the proposed cant

deficiency: (i) No wheel of the vehicle type unloads to a value less than 60 percent of its static value

on perfectly level track; and

(ii) For passenger cars, the roll angle between the floor of the equipment and the horizontal does not exceed 8.6 degrees;

or

(2) When operating through a constant radius curve at a constant speed corresponding to the proposed cant deficiency, and a test plan is submitted and approved by FRA in accordance with § 213.345 (e) and (f):

(i) The steady-state (average) load on any wheel, throughout the body of the curve, is not less than 60 percent of its static value on perfectly level track; and

(ii) passenger cars, the steady state (average) lateral acceleration measured on the floor

of the car body does not exceed 0.15g

4.4 Stipulations of EN-14363: (9)

The UIC Sub-Committee 12 has recommended specific operational parameters for application

during the testing of running behaviour for international traffic. Thus, the permissible cant

deficiencies Cdadm shall be imposed according to Table G.1 for the indicated

- Train types - Vehicles - Track conditions and - Maximum permissible speeds of the vehicle Vadm.

Table G.1- Recommended operational parameters

Types of Train

Vehicles 1) Infrastructure Maximum permissible

speed of the vehicle Vadm in km/h

Permissible cant deficiency Cd adm in mm

Freight Train

Conventional freight wagons

Conventional Infrastructure

≤ 120 130

Suitable conventional freight wagons

120… ≤ 140

Specific freight wagons 140… ≤ 160 150

Passenger Train

Conventional passenger coaches and motor coaches

≤ 230

Specific motor coaches and multiple units

≤ 160 165

160…≤ 250

150 Upgraded high speed line

200……≤ 250

High-speed slab track line

250……≤ 300 130

150

Vehicles with special equipment for the negotiation of curves

≤ 300 According to specific definition

4.4 Stipulation of UIC-518: (8)

(i) Passenger trains (conventional design)

Cd = 150 for V ≤ 230 kmph

(ii) Non tilting MV and rail cars with special features (e.g. low CG, low axle loads)

(a) Conventional lines, Cd = 150 for 230 ≥ V > 160,

Cd = 165 for V ≤ 160

(b) High Speed Lines, Cd = 150 for 250 ≥ V > 200,

4.5 Thus, the design of Rolling stocks and Maintenance regime is important factor while deciding the permissible cant deficiency. Suitable guidelines in this regard are to be laid down by Rolling stock engineers for suitability for Higher Cant deficiency. 5.0 EFFECT OF HIGHER CANT DEFICIENCY ON TRACK DESIGN & LAYOUT:

5.1 Length of Transition curve

One important issue to be dealt in connection with increasing permissible cant deficiency to allow for

higher speed is length of transition curve.

Table given below shows the criteria stipulated for Broad gauge track for calculation of required transition curve length:

(6)

Criteria for length of transition curve

Desirable length of the transition curve

Minimum length of the transition curve

(a) From consideration of rate of change of cant as 35mm/sec for normal cases & 55 mm/sec for exceptional cases.

Ca × Vm

125 = 0.008 Ca × Vm

Ca × Vm

198

= 0.005Ｃa

(b) From consideration of rate of change of cant deficiency as 35mm/sec for normal cases & 55 mm/sec for exceptional cases.

Cd × Vm

125 = 0.008 Cd × Vm

Ca × Vm

198

= 0.005Ｃd

(c) From consideration of cant gradient

Cant gradient not to exceed 1 in 720

Cant gradient not to exceed 1 in 360 for BG & 1in 720 for MG & NG

Considering an example of 1.5º curve, laid with cant of 80mm and considering the cant deficiency as 75 mm, the required transition length will be as calculated below: L1 = 0.008 x 80 x 140 = 89.6m L2 = 0.008 x 75 x 140 = 84 m L3 = 0.72 x 80 = 56 m In this case, the cant provided has become the governing factor for deciding length of transition curve. Length of Transition curve kept according to this cant, will restrict the maximum permitted cant deficiency also equal to the cant value i.e. 80mm, considering the permissible rate of change of cant deficiency as 35 mm/s, same as that of cant. To permit higher cant deficiency on such curves, rate of change of cant deficiency will have to be kept higher than 35 mm/s. However, length of transition curves already reduced with the considerations of higher rate of change of cant deficiency will restrict this option also. 5.2 Design of Track Components: The unbalanced lateral acceleration caused due to cant deficiency exerts a lateral force, proportional to axle load, on track components. This lateral force will be supplemented by LWR force and dynamic load, the magnitude being directly related to state of maintenance of track and vehicle. The design of track components should be checked for this lateral force. As per studies

(3) in RDSO Report C-147, the

maximum observed lateral force was 6.1t at 120 kmph whereas maximum assessed value was 6.3t. This is considered to be well within the design limits. The increase in rail stresses observed due to maximum on loading was also found within limits as per studies in RDSO Reports C- 106

(2) & C- 147

(3).

6.0 PRESENT SCENARIO IN INDIAN RAILWAYS

6.1 The cant deficiency of 100 mm is permitted for nominated rolling stock on nominated high speed

routes. The Rolling stock has been decided based on results of oscillation trials with 100 mm cant

deficiency.

6.2 Rolling Stocks cleared for 100 mm cant deficiency on Indian Railways:

Following are the some rolling stocks which have shown satisfactory behaviour during oscillation trials conducted at speeds 130 kmph and above, stipulating 100 mm cant deficiency on routes where track is maintained to improved standards: • WDP1, WDP2, WDP3, WDP4, WAP1, WAP3, WAP5, WAP6 and WAM4 locomotives • LHB Coaches – CC, AC 3 Tier, AC 2 Tier, First AC, Sleeper, Pantry Car, Generator Van • Few ICF All Coil Suspension Coaches

7.0 CONCLUSION AND RECOMMENDATION

7.1 The studies conducted by RDSO earlier with ICF coaches, WDM4 & WDM2 locomotives indicate

that a cant deficiency of the order of 100mm does not result in to any large values of wheel off-

loading and on-loading, lateral forces or lateral accelerations. The various stresses on the track,

the derailment and track distortion coefficients also have remained within the acceptable limits on a

well maintained track.

7.2 The results of various oscillation trials conducted over different rolling stocks stipulating cant

deficiency of 100 mm also confirm this aspect on well maintained Track.

7.3 On track maintained to normal standards, the studies have not been done to assess the effect of

higher cant deficiency. However, with almost uniform track structure and machine maintenance,

the results are not likely to be at much variance with the available results. This observation needs

to be confirmed by limited studies.

7.4 As a part of limited studies, it has been considered that all future oscillation trials will be undertaken

stipulating 100 mm cant deficiency on all routes of Indian Railways for locos and coaches to

ascertain the behaviour.

7.5 The cant deficiency of 100 mm as permissible now, shall be made use of for The locomotives and

coaches, for which oscillation trials have been successfully completed stipulating 100 mm cant

deficiency on high speed routes. However, it shall be checked that rate of change of cant

deficiency should not exceed the limit of 55mm/s as per existing stipulations.

7.6 The rolling stock engineers shall clearly lay down the design criteria for deciding the capability of

rolling stock for operation at higher cant deficiency in line with international practices.

7.7 Based on inputs available, it is observed that with collaborative effort of track and rolling stock

designers, it shall be possible to permit higher cant deficiency of about 125 mm on all Broad

Gauge routes of Indian Railway without any major input. However, studies in this regard will be

required. This will facilitate relaxation of speed restrictions on curves on existing track and new

tracks can be designed with lower cant for reduced wear.

7.8 To begin with, the effort is being made to permit cant deficiency of 100 mm on all routes based on

the results of studies and oscillation trials.

.................................. xxx ......................................

Bibliography:

1. RDSO Report C&M Vol-I: Increase of speed on Delhi-Howrah route; Feasibility study

2. RDSO Report C-106: Effect of Cant Deficiency on Distribution of Vertical and Lateral Loads on the Inner and Outer Rails of a Curve: Trials conducted with WDM4 Loco and ICF Coaches upto 120kmph on 2

0 curve (cant deficiency of 145mm).

3. RDSO Report C-147: Effect of Cant Deficiency on distribution of lateral and vertical forces on the inner and outer rails of a curve: Trials conducted with WDM2 Loco upto 120kmph on 2

0

curve (cant deficiency of 145mm).

4. Modern Railway Track: Coenraad Esveld

5. IRICEN Publication – Speed on Curves

6. Indian Railway Permanent Way Manual

7. AREMA (American Railway Engineering and Maintenance of Way Association) 2010, Manual for Railway Engineering (Vol. 1); Track

8. UIC CODE 518: Testing and approval of railway vehicles from the point of view of their dynamic behavior – Safety – Track fatigue – Running behavior

9. EN 14363: Railway application – Testing for acceptance of running characteristics of railway vehicles – Testing and running behavior and stationary tests

10. FEDERAL REGISTER, Vol 78, No 49, Part II, Department of Transportation, Federal Railroad Administration, 49 CFR Parts 213 and 238: Vehicle/Track Interaction Safety Standards; High-Speed and High Cant Deficiency Operations; Final Rule