4.1.5 Guard Rails and Guard Timbers

Prototype Information

A guard-rail is a longitudinal member, usually second-hand track-rails, placed eight to ten inches inside the rail to hold the wheels in their proper position on the rails or to guide derailed wheels. Guard-­rails are used on bridges and trestles, in tunnels, at derailing switches, at bridge expansion-joints in the track, on sharp curves, and opposite all frogs. 

Crossing

Turnout

Bridge

A guard timber is a longitudinal member, usually placed outside the rails at the ends of the ties, on open-floor or ballasted deck bridges. They are used to properly space the ties and hold them in place.

  Function. Guard-rails and guard timbers have two functions. First, they are used to guide wheel flanges through crossings,  Second, they are used to used to force the direction of wheel flanges through turnout frogs or derails. Third, they are used to protect bridges and structures from damage by derailed wheels by trapping the wheels and keeping the locomotive or car on the bridge.  

Engineering.

Crossings and turnouts.  

Guard rails are steel rail, the same rail size as the main rail. They are bolted to the main rail and spiked to the tie with special tie plates. See 4.1.7 Special works for construction and additional information.

Bridges. 

There are no strict rules governing the use of guard rails. 

1. Generally guard-rails are employed on any track where girders, trusses or other supporting members of the protected structure project above the rail.
2. Guard rails are steel rail, usually near the end of their service life or designated as scrap. They are either the same rail size as the main rail, or one size smaller. They are located eight to ten inches inside the track gauge, fully spliced at joints and spiked to at least every second tie. 
3. Rail-braces may be placed on every second or third tie on the track-center side, per common standard.
4. The guard-rails are extended from the protected structure at various lengths depending on the right-of-way engineering standards and are terminated at a determined minimum distance. On single track main lines guard-rails may be run out a distance of 50 feet minimum each way from the protected structure. For bridges the start of the runout is the face of the abutment back wall. If a protected structure is located near a curve in the right-of-way, the distance may be expanded to 100 feet or more.
5. Double track main lines and bridges will have a guard rail only the outside rail on the outside tracks. 
6. When multiple bridges are connected the bridge guard-rails will be continuous between bridges.

Guard-rails are usually terminated by converging the two rails to the track center line. This is to prevent brake rigging from catching on the exposed ends. The convergence begins 21 feet before the guard-rail end. The convergence rails must be continuous - no joints. The ends of the guard-rails may be:

1. Bent down to clear the top of ties.  
2. Planed to tapering edges and bolted together. 
3. Bolted to and protected by a point (wedge-shaped) casting.

Bent Down

Tapered Point

Point Casting

  Guard rails employed on double track main lines with traffic in one direction only, may choose to terminate the approach end (as above) and terminate the other end without curving, bending, or tapering.

 Guard-timbers

Guard-timbers are located outside the track gauge. The timber size is generally 6" x 8 ", and 'dapped' (mortised) to hold the bridge ties in alignment. Guard rails are bolted to every third or fourth tie per common standard. When the inner guard-rails adequately spaced with relation to the track-rails, the derailed wheels will strike the guard-rail without striking the guard­-timber.

Usage by NW regional railroads

Great Northern. Guard-rail was used rail, bulb angle and timber. Guard timber is 8"x6" (10"x3" by 1953), dapping 1.5". Used on all through and deck bridges and trestles over 30 feet in height. Not used on timber trestles. Used only in timber lined tunnels.

Northern Pacific. Guard-rail was used rail, Guard timber is 8"x6", dapping 1.5". Used on all through bridges, deck bridges more than 100 feet in length and more than 30 feet in height. Used on timber bridges more than 100 feet in length and on certain bridges on curves less than 100 feet in length. Only used when through bridge is near tunnel portal or timber snow sheds when located at the end of a tunnel.

Milwaukee Road. Initially composite guard-rail was 6"x4.5" angle iron and 6"x4" timber. Later used rail. Guard timber initially 10"x12", later is 8"x6", dapping 1.5". Used on bridges more than 200 feet on tangent track, and all bridges on curved track. At overpasses and structures at owners request.

Union Pacific. Guard timber is 8"x6" (8"x5" on light traffic lines), dapping 1.5". Used on all through or deck truss bridges, all through girder more than 30 feet in length, and all deck girder bridges or trestles 150 feet long. Used at supports of overpasses or other structures adjacent to main track. Used in all tunnels.

The WWSL

The WWSL Common Standard is to maintain guard rails on all bridges, crossings and tunnels, and at points where supporting members of structures project above the rail. 

• On mainline bridges thirty feet or more in length and on side track bridges 60 feet or more in length on tangent tracks.
• On all bridges 20 feet or more in length or within three hundred feet of a curve in the normal direction of traffic.
• Installed in all timber lined tunnels.
• The weight of the guard-rail shall be not more than 10 pounds per yard less than the weight of the running rail except 
• Guard-rail is run out a distance of 50 feet minimum each way from guarded structure. 

The OPLC Common Standard is to maintain guard rails on all bridges, and will have guard-rails installed on certain sharp curves.

 

The STC Common Standard is to maintain guard rails on the chip unloading track and the chemical unloading track. 

Modeling Information 

See 4.1.7 Special works for Crossing construction details.

See 4.1.6  Turnouts for Turnout construction details.

See 4.1.9C Bridge Details for Bridge construction details.