Part D – Design Calculations

• 10. Design Considerations
• 11. Location of Grade Crossings

10. Design Considerations

10.1 Clearance Distance (cd)

10.1.1 Clearance Distance (cd) is the distance between the clearance point in advance of the grade crossing, to the clearance point beyond the farthest rail, as shown in Figure 10-1.

10.1.2 The clearance point is the point 2.4 m beyond the outside edge of the farthest rail from the departure point measured perpendicular to the rail.

10.2 Vehicle Travel Distance (s)

10.2.1 The total distance, in metres, the design vehicle must travel during acceleration to pass completely through the Clearance Distance (cd) is calculated using the following formula:

s = cd + L equation 10.2

where,

cd = Clearance Distance in metres; and

L = the total length, in metres of the design vehicle.

(a) For Grade Crossings with a Warning System or Railway Crossing Sign

Figure 10-1 (a) - Text version

Figure 10-1 has two diagrams with measurements and arrows illustrating the location of a signal or sign, clearance point, clearance distance, centerline of road, and direction of travel on a grade crossing.

The clearance point is the closest point on the departing lane of a grade crossing that is 2.4 m from the nearest rail measured perpendicular to the rail. The departure point of the clearance distance measurement is 2.0 m before the signal or sign.

Figure 10-1 (b) - Text version

The clearance point is the closest point on the departing lane of a grade crossing that is 2.4 m from the nearest rail measured perpendicular to the rail. The departure point of the clearance distance measurement is 2.0 m before the signal or sign. If there's no sign or signal, the starting point is at 5.0 m measured perpendicular from the nearest rail.

10.3 Departure Time - General

10.3.1 The Departure Time is the greater of the time required for the design vehicle to pass completely through the Clearance Distance (cd) from a stopped position (T_D) or the time required for pedestrians, cyclists and persons using assistive devices to pass completely through the Clearance Distance (cd) (T_P).

Table 10-1 Ratios of Acceleration Times on Grades must be used to account for the effects of road gradient on the design vehicle for the grade crossing. The established ratio of acceleration time (G) must be incorporated into the Acceleration Time (T) by multiplying the acceleration time on level ground (t) by the ratio of acceleration time (G).

10.3.2 Departure Time - Design Vehicle (T_D)

The total time, in seconds, the design vehicle must travel to pass completely through the Clearance Distance (cd) is calculated using the following formula:

T_D = J + T equation 10.3a

where,

J = the perception-reaction time, in seconds, of the crossing user to look in both directions, shift gears, if necessary, and prepare to start (must use 2 seconds at minimum); and

T = the time, in seconds, for the grade crossing design vehicle to travel through the Vehicle Travel Distance (s) taking into account the actual road gradient at the grade crossing.

T may be obtained through direct measurement or calculated using the following formula:

T = (t x G) equation 10.3b

where,

t = the time, in seconds, required for the design vehicle to accelerate through the Vehicle Travel Distance (s) on level ground established from Figure 10-2 Assumed Acceleration Curves; and

G = the ratio of acceleration time established from Table 10-1 Ratios of Acceleration Times on Grade or may be obtained through direct measurement.

10.3.3 Departure Time – Pedestrians, Cyclists and Persons Using Assistive Devices (T_P)

The total time, in seconds, that pedestrians, cyclists and persons using assistive devices must travel to pass completely through the Clearance Distance (cd) is calculated using the following formula:

T_p= cd / V_p equation 10.3c

where,

cd = the Clearance Distance, in metres (Article 10.1); and

V_p = the average travel speed, in metres per second (m/s), for pedestrians, cyclists, and persons using assistive devices (to a maximum value of 1.22 m/s).

10.4 Gate Arm Clearance Time

10.4.1 Gate Arm Clearance Time is the greater of T_{G ssd} or T_{G stop} and represents the time, in seconds, it takes the design vehicle to travel from either the Stopping Sight Distance (SSD) position or the Stop position to the point past the gate arm.

Gate Arm Clearance Time from SSD postion (T_{G ssd}) is calculated as follows:

T_{G ssd} = cd_{G ssd}/(0.27 x V_road) equation 10.3c

Where:

V_road = the road crossing design speed over the crossing in kilometres per hour (km/h); and

cd_{G ssd} = SSD + 2 m + L

where,

SSD is the stopping sight distance, in metres, and is calculated using the following formula:
SSD = 0.278 x 2.5 x V + d

1. d = braking distance (m)
2. V = initial speed (km/h)
3. L = the total length, in metres, of the design vehicle

Gate Arm Clearance Time from the Stop position (T_{G stop}) is calculated as follows:

T_{G stop} = J + (tcd_{G stop} x G)

where,

J = 2 seconds, and is the perception-reaction time, in seconds, of the crossing user to look in both directions, shift gears, if necessary, and prepare to start; and

G = the ratio of acceleration time established from Table 10-1 Ratios of Acceleration Times on Grade or may be obtained through direct measurement; and

tcd_{G stop} = the time, in seconds, required for the design vehicle to accelerate through the Gate Arm Clearance Distance (cd_{G stop}) on level ground established from Figure 10-2 Assumed Acceleration Curves; (Note; (cdG stop) is used in place of (s) and (tcd_{G stop}) is used in place of (t) from Figure 10-2)

where,

cd_{G stop} = 2 m + L

where,

L = the total length, in metres, of the design vehicle.

Figure 10-2 - Text version

In the graph, the acceleration time is plotted against the distance travelled during vehicle acceleration. Illustrated are the acceleration curves for; long load logging truck which shows an acceleration time of approximately 10 seconds to 20 seconds and travels a distance of approximately 15 meters to 67 meters, tractor trailers and long combination vehicles which shows an acceleration time of approximately 7 seconds to 18 seconds and travels a distance of approximately 14 meters to 90 meters, single units trucks which shows an acceleration time of approximately 6 second to 13 second and travels a distance of approximately 14 meter to 57 meter and passenger vehicles  which shows an acceleration time of approximately 4 second to 9 second and travels a distance of approximately 12 meter to 57 meter, based on the distance travelled during acceleration (meter) and the acceleration time (seconds)

Table 10-1 Ratios of Acceleration Times on Grades

Design Vehicle	Road Grade (%)
	-4	-2	0	+2	+4
Passenger Car	0.7	0.9	1.0	1.1	1.3
Single Unit Truck & Buses	0.8	0.9	1.0	1.1	1.3
Tractor-Semitrailer	0.8	0.9	1.0	1.2	1.7
Source: Geometric Design Guide for Canadian Roads, published by the Transportation Association of Canada and dated September 1999

Table 10-2 Road Design Specification for Road Approach

SPECIFICATIONS

Column A	Column B	Column C
Rural	Local	Divided
	Collector
Urban	Arterial	Not Divided
	Expressway
	Freeway

Table 10-3 Characteristics of Rural Roads

	Rural Locals	Rural Collectors	Rural Arterials	Rural Freeways
Service function	Traffic movement secondary consideration	Traffic and land access of equal importance	Traffic movement primary consideration	Optimum mobility
Land service	Land access primary consideration	Traffic movement and land access of equal importance	Land access secondary consideration	No access
Traffic volume vehicles per day (typically)	<1000 AADT	<5000 AADT	<1 2000 AADT	>8000AADT
Flow characteristics	Interrupted flow	Interrupted flow	Uninterrupted flow except at	free flow (grade separated) major intersections
Design speed (km/h)	50 – 110	60 - 110	80 – 130	100 – 300
Average running speed (km/h) (free flow conditions)	50 – 90	50 – 90	60 – 100	70 -110
Vehicle type	Predominantly passenger cars, light to medium trucks and occasional heavy trucks	All types, up to 30% trucks in the 3 t to 5 t range	All types, up to 20% trucks	All types, up to 20% heavy trucks
Normal connections	Locals collectors	Locals collectors arterials	Collectors arterials freeways	Arterials freeways
Source: Geometric Design Guide for Canadian Roads, published by the Transportation Association of Canada and dated September 1999

Table 10-4 Characteristics of Urban Roads

	Public Lanes Residential	Public Lanes Commercial	Locals Residential	Locals Indust./Comm.	Collectors Residential	Collectors Indust./Comm	Arterials Minor	Arterials Major	Expressways	Freeways
Traffic service function	Traffic movement not a consideration	Traffic movement not a consideration	Traffic movement secondary consideration	Traffic movement secondary consideration	Traffic movement and land access of equal importance	Traffic movement and land access of equal importance	Traffic movement major consideration	Traffic movement primary consideration	Traffic movement primary consideration	Optimum mobility
Land service/ access	Land access only function	Land access only function	Land access primary function	Land access primary function	Traffic movement and access of equal importance	Traffic movement and access of equal importance	Some access control	Rigid access control	No access	no access
Traffic volume (veh/day) (typical)	<500	<1000	<1000	<3000	<8000	1000-12 000	5000 – 20 000	10 000 – 30 000	>10000	<20 000
Flow characteristics	Interrupted flow	Interrupted flow	Interrupted flow	Interrupted flow	Interrupted flow	Interrupted flow	Uninterrupted flow except at signals and crosswalks	Uninterrupted flow except at signals and crosswalks	Uninterrupted flow except at signals	Free-flow (grade separation)
Design speed (km/h)	30-40	30-40	30 – 50	30 – 50	50 - 80	50 - 80	40-60	50-90	80 – 110	80- 120
Average Running speeds (km/h) (off-peak)	20 - 30	20 - 30	20 - 40	20 - 40	30 - 70	30 - 70	40 - 60	50 -90	60 - 90	70 – 110
Vehicle type	Passenger and service vehicles	All types	Passenger and service vehicles	All types	Passenger and service vehicles	All types	All types	All types up to 20% trucks	All types up to 20% trucks	All types up to 20% trucks
Desirable connections	Public lanes, locals	Public lanes, locals	Public lanes, locals, collectors	Public lanes, locals, collectors	Locals, collectors, arterials	Locals, collectors, arterials	Collectors, arterials, expressways, freeway	Collectors, arterials, expressways, freeway	Arterials, expressway, freeways	Arterials, expressways, freeways
Transit service	Public lanes, locals	Public lanes, locals	Public lanes, locals, collectors	Public lanes, locals, collectors	Locals, collectors, arterials	Locals, collectors, arterials	Express and local busses permitted	Express and local busses permitted	Express buses only	Express buses only
Accommodation of cyclists	No restriction or special facilities	No restriction or special facilities	No restriction or special facilities	No restriction or special facilities	No restriction or special facilities	No restriction or special facilities	Lanes widening or separate facilities desirable	Lanes widening or separate facilities desirable	prohibited	prohibited
Accommodation of pedestrians	Pedestrian permitted, no special facilities	Pedestrian permitted, no special facilities	Sidewalks normally on one or both sides	Sidewalks provided where required	Sidewalks provided both sides	Sidewalks provided where required	Sidewalks may be provided, separation for traffic lanes preferred	Sidewalks may be provided, separation for traffic lanes preferred	Pedestrian Prohibited	Pedestrian Prohibited
Parking (typically)	Some restrictions	Some restrictions	No restrictions or restrictions one side only	No restrictions or restrictions one side only	Few restrictions other than peak hour	Few restrictions other than peak hour	Peak hour restriction	Prohibited or peak hour restriction	prohibited	prohibited
Min. Intersection spacing1 (m)	As needed	As needed	60	60	60	60	200	400	800	1600 (between interchanges)
Right-of-way width (m) (typically)	6 - 10	6 - 10	15 - 22	15 - 22	20 - 24	20 - 24	202 - 453	202 - 453	>453	>603
Source: Geometric Design Guide for Canadian Roads, published by the Transportation Association of Canada and dated September 1999

11. Location of Grade Crossings

11.1  A public grade crossing where the railway design speed is more than 25 km/h (15 mph) must be constructed so that no part of the travelled way of an intersecting road or entranceway (other than a railway service road), is closer than 30 m (D) to the nearest rail of the grade crossing (see Figure 11-1).

Figure 11-1, Diagram 1

Figure 11-1, Diagram 1 - Text version

As provided for in article 11.1 a public grade crossing must be constructed so that no part of the travelled way of an intersecting road is closer than 30 m to the nearest rail of the grade crossing.

Figure 11-1, Diagram 2 - Text version

As provided for in article 11.1 a public grade crossing must be constructed so that no part of the travelled way of an entranceway (other than a railway service road), or the stop line or position of a traffic control device is closer than 30 m to the nearest rail of the grade crossing.