10. Design Considerations
Part D – Design Calculations
Grade Crossings Standards
- Printable Version
- Table of Contents
- Part A – Introduction
- Part B – Existing Grade Crossings
- Part C – New Standards
- Part D – Design Calculations
- Part E – Warning System Design
- Part F – Interconnected Devices
- Appendix A – Light Emitting Diode (LED) Signal Modules
- Appendix B – Limited Use Warning Systems
- Appendix C – Limited Use Warning Systems with Walk Light
- Appendix D – Whistling Cessation
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
Text version of Figure 10-1 a)
(b) For Grade Crossings without a Warning System or Railway Crossing Sign
Text version of Figure 10-1 b)
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.
Amended January 1, 2019 – in force March 1, 2019
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 10-1Ratios of Acceleration Times on Grade or may be obtained through direct measurement.
10.3.3 Departure Time – Pedestrians, Cyclists and Persons Using Assistive Devices (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
- d = braking distance (m)
- V = initial speed (km/h)
- 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 + (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,
cd_{G 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 (T_{G stop}) is calculated as follows:
T_{G stop} = J + (tcd_{G 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,
cd_{G stop} = 2 m + L
where,
L = the total length, in metres, of the design vehicle.
Figure 10-2 Assumed Acceleration Curves
Source: Geometric Design Guide for Canadian Roads, published by the Transportation Association of Canada and dated September 1999
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
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 spacing^{1} (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 | 20^{2} - 45^{3} | 20^{2} - 45^{3} | >45^{3} | >60^{3} |
Source: Geometric Design Guide for Canadian Roads, published by the Transportation Association of Canada and dated September 1999