Table Common AREMA Lateral Turnouts Currently in Use in Passenger Rail Systems

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1 DRAFT CHAPTER 11 SECTIONS , Part 3 Track and Roadway Considerations SECTION 3.5 TRACK AND ROADWAY CONSIDERATIONS Turnouts and Crossovers (2012) Turnouts and crossovers are used to permit trains to change between tracks. A turnout permits one track to split into two tracks. A crossover is formed of two turnouts placed back to back to permit train movements between parallel tracks. Standard plans of turnouts of various sizes can be found in the AREMA Portfolio of Trackwork Plans. Most railroads and passenger rail authorities also maintain their own books of standard turnout and crossover plans which slightly modify the AREMA plans Lateral Turnouts Turnouts are normally selected based on the desired diverging speed, frog angle, and the space available for the footprint of the turnout. These key characteristics are shown in Table below for lateral turnouts conforming to AREMA standards. Table Common AREMA Lateral Turnouts Currently in Use in Passenger Rail Systems TURNOUT NUMBER FROG ANGLE APPROXIMATE FOOTPRINT DIVERSION SPEED / / / /60 In terminal areas and yards and other locations where a diverging speed of 15 mph is acceptable, a Number 8, 9, 10, or 11 turnout may be used. It is preferred to use a Number 10 or 11, and to reserve Numbers 8 or 9 only for locations where a Number 10 or 11 will not fit. These turnout sizes are also commonly used for industrial sidetracks on main lines and branch lines. In certain existing terminals and yards, smaller turnout sizes down to a No. 6 or a No. 6.5 are in use with a permitted speed of 5 or 10 mph. Where possible, it is desirable to eliminate these smaller turnouts during reconstruction work due to the difficulties encountered by standard 85 ft. long passenger equipment traversing the diverging routes of these turnouts. The larger turnout sizes are used where higher diverging speeds are required, typically on mainlines away from stations or at through stations where space permits higher approach and

2 departure speeds from the platform area. The Number 20 turnout is the standard turnout used at the ends of passing sidings and for most crossovers. Number 15 turnouts are used where a Number 20 will not fit, or where a lower speed is acceptable, such as near a station where most trains will stop, or near a location with a permanent speed restriction, such as a sharp curve. Number 12 turnouts are used where a Number 15 turnout will not fit, but operational constraints require a speed higher than 15 mph. Number 24 turnouts are used to increase mainline capacity by eliminating the need for many trains to slow down for diverging routes at turnouts. They permit freight trains to diverge at 50 mph, and can permit passenger train speeds of 60 mph. Where diverging speeds at the upper end of Table or higher are required, the tangential turnout designs in Table should also be considered. Tangential geometry turnouts can also provide improved ride quality for passengers, through the diverging route, over conventional turnout designs Equilateral Turnouts Equilateral turnouts permit higher diverging speeds within the same footprint as a lateral turnout by splitting the frog angle between the two routes, resulting in the creation of two diverging routes on a gentler curve than the lateral turnout of the same number. As a rule of thumb, equilateral turnouts permit a diverging speed 50% higher than a lateral turnout. Because equilateral turnouts do not have a straight through route, they should not be used where the higher speed along the through route is required. Table provides the speeds of common equilateral turnout designs. Table Equilateral Turnouts Currently in Use in Passenger Rail Systems TURNOUT NUMBER DIVERSION SPEED / Tangential Turnouts See section above Other Geometric Considerations for Turnouts As noted in Section above, turnouts of the same hand placed point to point should be treated as a reverse curve for the purpose of geometric layout. It is desirable that they be spaced apart a distance of three times the diverging speed where possible, but at least one car length of 85 feet. Some constricted yard or terminal locations with low speeds will only permit short distances between back to back switch points. In these cases, a distance of less than 50 feet is sometimes used for No. 10 turnouts and larger. When No. 8 and 9 turnouts are placed closely point to point, distances of less than 50 feet are inadequate, and will cause passenger car

3 vestibule buffers to pass each other while the train negotiates the track, leaving an opening between cars. It should also be noted that No. 8 crossovers on track centers of less than 14-0, and No. 9 crossovers on track centers of less than 13-0 will also have reversing tangents between the frogs of less than 50 feet. For this reason, low number crossover layouts on tight track centers should be avoided. Turnouts of opposite hands placed point to point must be spaced sufficiently far apart to provide a short stretch of tangent between the bends in the stock rails that is long enough to accommodate the full length of a 6 wheel (3 axle) truck on an engine or car completely on the tangent. This distance should be taken as a minimum of 13 feet and may be required to be longer. The placing of turnouts on horizontal or vertical curves should ordinarily be avoided. For recommendations concerning the location of turnouts relative to horizontal curves, see Section above. Similar criteria should be used for the location of vertical curves near turnouts. In some cases, the location of a turnout on a horizontal or vertical curve cannot be avoided, or is an already existing condition which must be maintained or modified. Recommendations for these situations are given below. When a turnout is placed on a curve, the curve should be uniform through the turnout with a break in the curvature to permit the use of a straight turnout frog. The same principal holds for placement of turnouts on spirals. If the curve is less than 30 minutes, a standard turnout may be used and forced to the curve with lining equipment. Turnouts on curves greater than 30 minutes should be custom fabricated for the intended curvature. The lead length of a curved turnout is the same as a straight turnout and is measured along the curve of the inside rail between the point of switch and the point of frog so that most standard turnout components can still be used. The degree of curvature added to the through route of the turnout is either added or subtracted from the curvature of the diverging route depending on if the diverging route is to the low or high side of the curve respectively, thus affecting permissible speed in the diverging route. Where turnouts diverge to the low side of a curve, the diverging speed is greatly reduced. For example, a No. 15 turnout placed on a 4 curve will have an 8 diverging curve thus reducing the permissible diverging speed to 15 mph. If the curve the turnout is placed on is superelevated, it will have the same superelevation on both the straight and diverging routes. Where the diverging route is to the high side of the curve, the curve of the diverging route will have reverse superelevation. Because the FRA limits reverse superelevation in curves in its track safety regulations in 49 CFR Part 213, this may limit both the diverging speed of the turnout and the amount of superelevation placed in the curve and thus the permissible speed through the curve on the through route. Where it is necessary to place a turnout in a vertical curve, the curve should be limited to an r value of 0.10 or less to ensure smooth functioning of the switch points and any movable frog point and limit bending stresses imposed on the frog casting. If possible, any vertical curve placed in a turnout should be limited to the area between the heel of switch and the toe of frog, or beyond the heel of frog to the last long tie.

4 Crossing Diamonds (2012) Crossing diamonds are required at junctions of two lines where two or more tracks must cross each other at grade, but a junction of the rail lines cannot be created either with turnouts due to a high angle between the two tracks, or with one track passing over or under the other track using fixed structures due to physical or financial constraints. Speed through crossing diamonds is normally restricted to 60 mph or less. This limitation should be taken into account early in the design process of lines with higher maximum speeds to determine if the diamond places an unacceptable constraint on planned operations. In general, it is desirable to avoid crossing diamonds wherever possible due to the procurement and maintenance costs of diamonds, and the inherent operational danger of collisions between trains. Where crossing diamonds must be used, the following criteria should be adhered to. Where crossing diamonds have intersecting angles up to standard angles of frogs from turnouts can be used, such as a Number 9, 8, 5, or 4. This allows the use of end frogs and tie plates commonly fabricated for turnout sizes used in the rail and transit industry. For angles greater than 14 15, more common angles such as 30, 45, 60, or 90 should be used to promote standardization. However, more common intersection angles should not be used when they would require undesirable changes in existing geometry of the approach tracks to the diamond, such as reverse curves. Where the intersecting angle is below 5, a movable point crossing is required. In a movable point crossing, the center diamonds are replaced with knuckle rail switch points powered by one or two switch machines. Movable point crossings are normally designed using the angle of a standard Number 15 or 20 turnout. Movable point crossings may also be required in other situations involving the use of curved track geometry through the diamond. Crossing diamonds should be designed and installed with a level grade of 0.0% on both tracks. Diamonds installed on grades are subject to accelerated degradation of components over time due to displacement of the track from train forces. If at least one of the tracks is installed on a grade, the grade will also create cross-level in the other track. This cross-level must be limited to the amounts permitted by the railroad s maintenance criteria and FRA safety limits in 49 CFR Part 213. The crosslevel created by a non-level crossing should be runoff away from the crossing at the normal rate specified by the railroad. In no case should the runoff rate exceed FRA regulatory limits. Crossing diamonds should not be installed with vertical curves passing through the diamond. It is desirable to keep horizontal and vertical curves at least 100 feet away from the end of the crossing frog rail to help maintain alignment of the diamond. Where it is required that trains be able to change tracks at the crossing diamond, but a connecting track cannot be installed due to physical or geometric constraints, a single or double slip switch may be used. Slip switches should only be used with angles conforming to standard turnout sizes.

5 Standard plans of Crossing Diamonds at various intersecting angles and also with various degrees of horizontal curvature through the diamond and also of Slip Switches can be found in the AREMA Portfolio of Trackwork Plans. The AREMA Portfolio of Trackwork Plans also specifies when additional hardware must be used in the diamond, such as raised guard rails or movable center points Track Layouts and Interlocking Plants To be Developed

TECHNICAL MEMORANDUM

TECHNICAL MEMORANDUM Turnouts and Yard Tracks TM 2.1.8 Prepared by: Signed document on file 21 June 09 George Harris Date Checked by: Signed document on file 15 July 09 Thomas Carroll Date Approved by: