# 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.

Amended January 1, 2019 – in force March 1, 2019

### 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 = the Clearance Distance, in metres; and

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

Figure 10-1 – Clearance Distance (cd) for Grade Crossings

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

(b) For Grade Crossings without a Warning System or Railway Crossing Sign

## 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 (TD) or the time required for pedestrians, cyclists and persons using assistive devices to pass completely through the Clearance Distance (cd) (TP).

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 (TD)

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

TD = 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.

Amended January 1, 2019 – in force March 1, 2019

10.3.2 Departure Time - Design Vehicle (TD)

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

TD = 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 10-1Ratios of Acceleration Times on Grade or may be obtained through direct measurement.

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

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:

Tp= cd / Vp equation 10.3c

where,

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

Vp = 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 TG ssd or TG 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 (TG ssd) is calculated as follows:

TG ssd = cdG ssd/(0.27 x Vroad) equation 10.3c

Where:

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

cdG 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 (TG stop) is calculated as follows:

TG stop = J + (t 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

t = the time, in seconds, required for the design vehicle to accelerate through the Gate Arm Clearance Distance (cdG stop) on level ground established from Figure 10-2 Assumed Acceleration Curves;

where,

cdG stop = 2 m + L

where,

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

Amended January 1, 2019 – in force March 1, 2019

Gate Arm Clearance Time from the Stop position (TG stop) is calculated as follows:

TG stop = J + (tcdG stop x G) equation 10.4b

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 10-1Ratios of Acceleration Times on Grade or may be obtained through direct measurement; and

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

where,

cdG stop = 2 m + L

where,

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

Figure 10-2 Assumed Acceleration Curves

Table 10-1 Ratios of Acceleration Times on Grades

-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

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 Traffic movement secondary consideration Traffic and land access of equal importance Traffic movement primary consideration Optimum mobility Land access primary consideration Traffic movement and land access of equal importance Land access secondary consideration No access <1000 AADT <5000 AADT <1 2000 AADT >8000AADT Interrupted flow Interrupted flow Uninterrupted flow except at free flow (grade separated) major intersections 50 – 110 60 - 110 80 – 130 100 – 300 50 – 90 50 – 90 60 – 100 70 -110 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 Locals collectors Locals collectors arterials Collectors arterials freeways Arterials freeways