2014 University Transportation Center for Railway Safety REU Program: Roxxie Mann
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An Evaluation of the Geometric Designs of Grade Crossings
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2014 University Transportation Center for Railway Safety REU Program: Roxxie Mann
- 1. Roxxie Mann
- 2. • Highway-Rail Grade Crossings (HRGC) are locations where a transport axes crosses one or multiple railroad tracks at the same elevation (FHWA, 2014).
- 3. • At-grade crossings • Other crossings
- 4. • To enhance the driver’s view of the crossing the following are desired: o Right Angle Intersection of highway and tracks o No nearby intersections or driveways • Crossing should not be located on either highway or railroad curves. o Roadway curvature will compel drivers to concentrate on the curve of the road rather than the oncoming train. o Railroad curvature will obstruct the sight distance of oncoming traffic.
- 6. • Uneven Crossing Elevations • Skewed Crossing
- 7. • Individual o To evaluate the geometric profiles of each site, as well as establish the required sight distance, braking distance and stopping distance while taking into account the adjustment factor due to the approach grade to the intersection and effect of skew o To learn and understand MircroStation/Geopak to a level at which detailed geometric profiles of HRGC can be developed. o To state the difference between obtaining coordinates from Lidar data, Google Earth, and Original Design • Overall o Export coordinates into CarSim in order to simulate different “real-life” scenarios and further analyze results from a civil engineers perspective.
- 9. • Located on 84th St. just off of Highway 2. • Concern is sight distance • Omaha Public Power District Crossing o Average of 1 Train/day o Max. speed of 25 mph • Posted Speed limit is 50 mph • Imagery Date 5/2012
- 10. • Located southwest of David City, Nebraska • Issue is rough crossing • BSNF crossing o 1 Train/day o Max speed of 25 mph • Posted Speed Limit 60 mph • Imagery Date 3/2014
- 11. • Located southwest of Nebraska City • Two lane street with a low volume of traffic • Concern is sight distance • Union Pacific Railroad Crossing o 15 Trains/day o Max Speed of 50 mph • Posted Speed Limit is 50 mph • Imagery date 9/21/2012
- 12. • Located south of Agnew road on Hwy N-79 • Two lane street • Skewed crossing • Issue is sight distance • Union Pacific Railroad Crossing o Average of 2 Trains/day o Max. Speed of 40 mph • Posted Speed Limit is 60 mph • Imagery Date 5/2013
- 13. • Located east of Davenport • Two lane street runs over two parallel train tracks. o Roughly 12 ft apart • Issue is rough crossing • Union Pacific Railroad Crossing o 49 Trains/day o Max. Speed of 70 mph • Posted speed limit is 60mph • Imagery Date 9/2008
- 14. 𝐷 𝑇 = 𝑉𝑇 𝑉𝑣 𝐴 𝑉𝑣 𝑡 + 𝐵𝑉𝑣 2 𝑎 + 2𝐷 + 𝐿 + 𝑊 𝐷 𝑇 = 𝐴 𝑉𝑇 𝑉𝐺 𝑎1 + 𝐿 + 2𝐷 + 𝑊 − 𝑑 𝑎 𝑉𝐺 + 𝐽 Case A Case B
- 15. Train speed (mph) Case B Case A Departure from stop Moving vehicle in (mph) 0 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 5 127 77 62 55 52 51 51 51 52 53 55 56 58 60 62 64 10 255 155 123 110 104 102 101 102 104 106 109 112 116 119 123 127 15 382 232 185 165 156 153 152 153 156 160 164 169 174 179 185 191 20 509 310 247 220 208 203 203 205 208 213 219 225 232 239 246 254 25 637 387 309 275 260 254 253 256 260 266 273 281 290 299 308 318 30 764 465 370 331 312 305 304 307 312 319 328 337 347 358 370 381 35 891 542 432 386 365 356 355 358 364 373 382 393 405 418 431 445 40 1019 619 494 441 417 407 405 409 416 426 437 450 463 478 493 508 45 1146 697 556 496 469 458 456 460 468 479 492 506 521 537 554 572 50 1273 774 617 551 521 509 507 511 520 532 546 562 579 597 616 635 55 1401 852 679 606 573 559 557 562 572 585 601 618 637 657 678 699 60 1528 929 741 661 625 610 608 614 624 639 656 675 695 717 739 763 65 1655 1007 803 716 677 661 659 665 676 692 710 731 753 776 801 826 70 1783 1084 864 771 729 712 709 716 728 745 765 787 811 836 862 890 75 1910 1161 926 826 781 763 760 767 780 798 820 843 869 896 924 953 80 2037 1239 988 882 833 814 811 818 832 852 874 899 927 956 986 1017 85 2164 1316 1050 937 885 865 861 869 884 905 929 956 985 1015 1047 1080 90 2292 1394 1111 992 937 915 912 920 936 958 983 1012 1042 1075 1109 1144 0 200 400 600 800 1000 1200 1400 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 SightDistanceRequired(ft) Train Speed (mph) Case A: Moving Vehicle (mph) 10 mph 15 mph 20 mph 25 mph 30 mph 35 mph 40 mph 45 mph 50 mph 55 mph 60 mph 65 mph 70 mph 75 mph 80 mph 120 240 361 481 601 721 842 962 1082 1202 1322 1443 1563 1683 1803 1924 2044 2164 0 500 1000 1500 2000 2500 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 SIGHTDISTANCEREQUIRE(FT) TRAIN SPEED (MPH) CASE B: DEPARTURE FROM STOP 0.00 5000.00 10000.00 15000.00 20000.00 25000.00 30000.00 0 10 20 30 40 50 60 70 80 90 DistancealongHighwayfromcrossing(ft.) Train Speed (mph) Sight Distance Leg along the Highway
- 16. • Case A-Intersections with no control • Case B-Intersections with stop control on the minor road o Case B1-Left turn from the minor road o Case B2-Right turn from the minor road o Case B3-Crossing maneuver from the minor road • Case C-Intersections with yield control on the minor road o Case C1-Crossing Maneuver from the minor road o Case C2-Left or right turn from the minor road • Case D-Intersections with traffic signal control • Case E-Intersections with all-way stop control • Case F-Left turns from the major roads The recommended dimensions of the sight triangles vary with the type of traffic control used at the intersection. Intersection Control
- 17. HWY 4 –L HWY 92- L & R HWY 79- L & R 84th- L & R HWY 4 - R King Rd - L King Rd-R
- 18. Design Speed (mph) Length of Leg (ft) HWY 4 HWY 92 HWY 79 84th St. King Rd. -3% +4% 0% 0% .5% -.5% -2.5% +1% -4% -6% 15 70 70 70 70 70 70 70 70 70 70 77 20 90 90 90 90 90 90 90 90 90 90 99 25 115 115 115 115 115 115 115 115 115 115 126.5 30 140 140 140 140 140 140 140 140 140 140 154 35 165 165 148.5 165 165 165 165 165 165 181.5 181.5 40 195 195 175.5 195 195 195 195 195 195 214.5 214.5 45 220 220 198 220 220 220 220 220 220 242 242 50 245 245 220.5 245 245 245 245 245 245 269.5 294 55 285 285 256.5 285 285 285 285 285 285 313.5 342 60 325 325 292.5 325 325 325 325 325 325 357.5 390 65 365 365 328.5 365 365 365 365 365 365 401.5 438 70 405 405 364.5 405 405 405 405 405 405 445.5 486 75 445 445 400.5 445 445 445 445 445 445 489.5 534 80 485 485 436.5 485 485 485 485 485 485 533.5 582 0 100 200 300 400 500 600 700 0 10 20 30 40 50 60 70 80 90 Lengthofleg(ft.) Design Speed (mph) Modified Sight Distance with Adjustment Factor on Approach Grade -6% -4% -3% to 3% 4%
- 19. Modified Stopping Sight Distance Design Speed (mph) Brake Reaction Distance (ft) Braking Distance on Level (ft) Stopping Sight Distance Downgrades Upgrades Calculated (ft) Design (ft) 3% 6% 9% 3% 4% 6% 9% 15 55.13 21.60 76.72 80 78.7 81.2 84.2 74.9 74.5 73.5 72.3 20 73.50 38.39 111.89 115 115.5 119.8 125.2 108.8 107.9 106.2 103.9 25 91.88 59.99 151.86 155 157.4 164.3 172.7 147 145.6 142.9 139.5 30 110.25 86.38 196.63 200 204.6 214.5 226.6 189.7 187.6 183.8 178.8 35 128.63 117.58 246.20 250 257.1 270.5 287 236.7 233.9 228.8 221.9 40 147.00 153.57 300.57 305 314.8 332.3 353.9 288.2 284.5 277.8 268.8 45 165.38 194.36 359.74 360 377.8 399.9 427.2 344 339.4 330.9 319.6 50 183.75 239.96 423.71 425 445.9 473.3 506.9 404.3 398.6 388.1 374.2 55 202.13 290.35 492.47 495 519.4 552.5 593.2 469 462.1 449.4 432.4 60 220.50 345.54 566.04 570 598.1 637.4 685.9 538.1 529.9 514.7 494.6 65 238.88 405.52 644.40 645 682 728.2 785.1 611.6 602 584.2 560.5 70 257.25 470.31 727.56 730 771.2 824.7 890.7 689.6 678.4 657.8 630.3 75 275.63 539.90 815.52 820 865.6 927.1 1002.9 771.9 759.1 735.4 703.9 80 294.00 614.29 908.29 910 965.2 1035.2 1121.4 858.6 844.1 817.1 781.3 𝑑 𝑟 = 1.47𝑉𝑡 𝑑 𝑏 = 1.075 𝑉2 𝑎 𝑑 𝑏 = 𝑉2 30( 𝑎 ± 𝐺) 0.00 200.00 400.00 600.00 800.00 1000.00 1200.00 0 10 20 30 40 50 60 70 80 90 Distance(ft.) Design Speed (mph) Brake Reaction Distance Braking Distance on Level Stopping Sight Distance -3% -6% -9% 3% 4% 6% 9%
- 20. 𝑡90 = 2𝑊1 𝑎 𝑡 𝑠𝑘𝑒𝑤 = 2𝑊2 𝑎 𝑡90 = 2.74 𝑠 Angle Street width (ft) (ft.) time of skew Change in time 84th St 80 17 17.10 2.75 0.01 HWY 79 32 17 30.83 3.69 0.95 HWY 92 38 17 57.36 5.03 2.29 King Rd 80 17 17.10 2.75 0.01 HWY 4 120 17 29.28 3.60 0.86
- 21. 𝐼𝑆𝐷 = 1.47𝑉𝑡 𝑔 𝑡 𝑔= time gap at design speed Passenger car 6.5 s plus the effect in skew value Design Speed (mph) Stopping Sight Distance (ft) Intersection sight distance for passanger cars with skewed and approaching grade factors HWY 4 (skewed) HWY 92 (skewed) HWY 79 (skewed) 84th St (skewed) King Rd (skewed) L -3% R 4% L 0 % R 0% L .5% R .5% L 2.5 % R -2.5% L -4% R- 6% 15 80 162.29 162.29 193.82 193.82 164.27 164.27 143.55 143.55 143.55 157.90 20 115 216.38 216.38 258.43 258.43 219.03 219.03 191.39 191.39 191.39 210.53 25 155 270.48 270.48 323.03 323.03 273.79 273.79 239.24 239.24 239.24 263.17 30 200 324.58 324.58 387.64 387.64 328.55 328.55 287.09 287.09 315.80 315.80 35 250 378.67 340.80 452.25 452.25 383.30 383.30 334.94 334.94 368.43 368.43 40 305 432.77 389.49 516.85 516.85 438.06 438.06 382.79 382.79 421.07 421.07 45 360 486.86 438.18 581.46 581.46 492.82 492.82 430.64 430.64 473.70 473.70 50 425 540.96 486.86 646.07 646.07 547.58 547.58 478.49 478.49 526.33 574.18 55 495 595.06 535.55 710.67 710.67 602.33 602.33 526.33 526.33 578.97 631.60 60 570 649.15 584.24 775.28 775.28 657.09 657.09 574.18 574.18 631.60 689.02 65 645 703.25 632.92 839.88 839.88 711.85 711.85 622.03 622.03 684.23 746.44 70 730 757.34 681.61 904.49 904.49 766.61 766.61 669.88 669.88 736.87 803.85 75 820 811.44 730.30 969.10 969.10 821.36 821.36 717.73 717.73 789.50 861.27 80 910 865.54 778.98 1033.70 1033.70 876.12 876.12 765.58 765.58 842.13 918.69 0 200 400 600 800 1000 1200 0 10 20 30 40 50 60 70 80 90 StoppingSIghtDistance(ft) Design Speed (mph) Intersection Sight Distance for Passanger Cars with Skewed and Approach Grade Factors Stopping Sight Distance HWY 4 Left/West Approach-3% HWY 4 Right/East Approach 4% HWY 92 Left/West Approach 0% HWY 92 Right/East Approach 0% HWY 79 Left/West Approach .5% HWY 79 Right/East Approach .5% 84th St Left/West Approach 2.5% 84th Right/East Appraoch -2.5% King Rd Left/West Approach -4% King Rd Right/East Approach -6%
- 22. • Which way would be the best to obtain a test site coordinates (horizontal, vertical and elevation) and create a 3D model? o LIDAR o Google Earth o Original Design
- 24. Google Earth Image from 2009 Site picture 2014
- 27. RR RR Xing @ 184+00.75 TT=1613.46 ft @ Sta. 184+00.75 Centerline of Hwy 4 Existing
- 29. • Regarding Part one o For each test site, intersections with no traffic signals and traffic signals on minor road (roadway) • sight distance • stopping distance • braking distance • consideration of different approaching grade (from left and right) • the effect of the skew • Regarding Part two o Google Earth • The most efficient way to retrieve coordinates and build 3D models o Original Design Plans • Gave a more realistic and the exact elevation, resulting in a more precise evaluation when discovering the vehicle’s dynamic profile after exported into CarSim
- 30. • Federal Highway Administration Safety Program (FHWA). (2013). "Railway-Highways Crossing (Section 130) Program." U.S. Dept. of Transportation, Washington D.C. • Federal Railroad Administration (FRA). (2010). "Highway-Rail Grade Crossings Handbook." U.S. Dept. of Transportation, Washington D.C. • Gillespie, Thomas D. (2004). "CarSim Data Manual." Mechanical Simulation Corporations, Michigan. • Montana Department of Transportation (MDOT). (2012). “Introduction to GeoPak MDT Road Design V8i SS2.” Civil Engineering Infrastructure Design & Road Design Software. Montana Department of Transportation, Montana. • Ogden, Brent D. Railroad-highway Grade Crossing Handbook. Washington, DC: U.S. Dept. of Transportation, Federal Highway Administration, 2007. Print. • Tennessee Department of Transportation (TDOT). (2009). "MicroStation V8." 3D CAD Design & Modeling Software. Tennessee Dept. of Transportation, Tennessee.
Editor's Notes
- HRGC are locations where transport axes crossed one or multiple railroad tracks at the same elevation. These transport axes can vary from roads to sidewalks. This picture illustrates active warning signals, and the intersection of the road and tracks are perpendicular to each other.
- There’s two different types of HRGCs. You have the at-grade crossings and other crossings. The two pictures above illustrates at-grade crossings and the two pictures below illustrates an other crossing. As you can tell the other crossings are intersections that have different elevations. The image on the left is a gravel road with ramps at the rails and the image on the right is a underpass of a road and overpass of railroad tracks.
- If practical, the highway should intersect the tracks at a right angle with no nearby intersections or driveways. This layout enhances the driver’s view of the crossing and tracks, reduces conflicting vehicular movements from crossroads and driveways. To the extent, crossings should not be located on either highway or railroad curves. Roadway curvature constrains a driver’s view of a crossing ahead, and a driver’s attention may be directed towards negotiation the curve rather than looking for a train. Railroad curvature may obstruct a driver’s view down the tracks from both a stopped position at the crossing and on the approach to the crossing. Crossing that are located on highway and railroad curves present maintenance challenges and poor rideability for highway traffics due to conflicting super elevation.
- It is ideal to have the intersection of a highway and railroad at the same level to provide a good viewing for sight distance, braking and acceleration distance as well as providing ride ability (comfort). There's two constraints that often apply to the maintenance of the grade crossing profiles: (i) drainage requirements and (ii) resource limitations. Vertical curves should be sufficient length to provide an adequate view of the crossing. To prevent drivers of low-clearance vehicles from becoming caught on the tracks, the crossing surface should be at the same plane as the top of the rails for a distance of 2 ft outside of the rails. The surface of the highway should also not be more than 3 in higher or lower than the top of the nearest rail at 30 ft from the nearest rail.
- Uneven Crossing Elevations: This occurs when either the roadway or railroad tracks are placed after the existence of the other resulting in a situation where the elevations are different. That is, the roadway is higher than the railroad tracks. This causes vehicles passing over the HGRC to experience a bump and cause discomfort to the occupants. Skewed Crossings: A skewed crossing refers to a situation when the railroad track and roadway are not perpendicular but rather at an acute angle from each other. This may result in (i) the wheels of a vehicle reaching and subsequently crossing the railroad tracks at different times resulting in discomfort to the occupants of the vehicle, and (ii) the issue of sight obstruction or inadequate sight distance.
- This project has it’s own analysis involving the geometrics of each HRGC. It’s also used as the base part to a colleague's project. This project as an individual has an objective of learning MicroStation to a level at which detailed geometric profiles of HRGC can be developed while being able to establish the difference between obtaining coordinates from lidar data, google earth and the original design plan. The overall objective of ths project is to correlate with a colleague's project by exporting data from mircostation into CarSim to simulate different scenarios to each test site.
- This is an over view of the five test sites provided by Nebraska Department of Roads. They are all located on the south east part of Nebraska.
- Test site 1 is the HRGC on 84th st in Lancaster county. This intersection is just south west of highway 2. It’s a two lane roadway at an angle of 80 degrees to a single set of train tracks. The main concern here was sight distance. This crossing is a part of Omaha public power district and averages 1 train a day with a maximum speed of 25 mph. The posted speed limit for 84th st is 50 mph. and this image was updated in 2012 by google earth.
- Test site 2 is a HRGC on Highway 92 in bulter county; It’s located just south west of david city, Nebraska. It’s a two lane roadway and runs at an angle across the set of tracks. The issue here is rough crossing. It’s a BSNF crossing with an average of 1 train per day with a maximum speed of 25 mph. The posted speed limit for traffic is 60 mph. This image was update through google earth in 2014
- Test site 3 is located on King Road in Otoe County southwest of Nebraska City. It’s a two lane road way with a low volume of traffic. The concern here is sight distance. It’s part of the Union pacific railroad crossing with an average of 15 trains a day with a maximum speed of 50 mph. The posted speed limit here is 50 mph and the image was updated in 2012
- Test site 4 is located on Hwy 79 in Lancaster County just south of Agnew road. It’s a two lane street that runs at an angle across the set of tracks. Issue here is sight distance. It’s a part of Uniion Pacific Railroad crossing with an average of 2 trains per day with a maximum speed of 40 mph and the posted speed limit is 60 mph. Image 2013
- Test site 5 is located east of davenport on hwy 4 in Thayer county. It’s a two lane street that crossing two parallel train tracks, roughly 12 ft apart from each other. The issue here is rough crossing. Union Pacific railroad crossing with an average of 49 train per day with a maximum speed of 70 mph. The posted speed limit is 60 mph. From the image shown on Google Earth we decided to have this test site as our main focus since right off the back you can tell that the crossing is extremely uneven and probably provides discomfort to occupants in vehicles crossing over the tracks.
- There’s 4 aspects regarding sight distance: the sight distances required for stopping, the sight distance required for passing, the sight distance required for complex locations and the sight distance required to meeting the criteria in designing. There’s two cases involving sight distance (Case A) a moving vehicle to safely cross or stop at railroad crossing (Case B) the departure of a vehicle from stopped position to cross railroad tracks. Here we have the Vs as the velocity of the object such as train, vehicle, the maximum velocity of a vehicle at first gear. The rest are constants. A=1.47 B=1.075 t=reaction time 2.5s a=driver’s deceleration 11.2 ft/s^2 D=distance of stop line 15ft De=distance from driver to front of vehicle 8ft L=Length of vehicle 73.5ft W=distance between rails 5ft J=time to activate clutch 2 s Da=distance vehicle travels in max speed in 1st geat 26.3 ft
- For HWY 79 with a max speed of 60 mph and max speed of a train at 40 mph the sight distance needed is 444 ft. For hwy 92 with a max speed of 60 mph and a max speed of a train at 25 the sight distance required is 278 ft. For hwy 4 with a max speedo f 60 mph and a max speed of a train at 70 mph the sight distance needed is 777 ft. For 84th street with a max speed of 50 mph and a max speed of a train of 25 mph the sight distance requied is 262 ft. For king road with a max speed of 50 mph and a max speed of a train at 50 mph the sight distance needed 524 ft. Now these values are the distances needed from the intersection the train traveling at that certain speed for that certain speed of the vehicle. Here you will notice that as the speed of the train increases the sight distance required will also increase with each speed of the vehicle. Basically a linear effect. The same for case B of the departure of a stopped vehicle. Now since most of these test sites are skewed crossing these sight distance values will change slightly depending on the angle of intersection.
- Regarding skewed crossing, there are different types of cases depending on the traffic control used at the intersection. For the purpose of this project, case A and Case B will be used with the minor road being the roadway and the major road being the railroad tracks.
- Here are the different adjustment factors that are needed to be taken into account when considering sight distance when grade exceeds 3%. For each test site there is two approach grades to consider (i) is the approach grade from left side, or west side the (ii) is the approach grade from the right side or east side. King road has two different adjustment factors to consider since the left and right side decrease in elevation at different rates as its approaching the intersection. The same goes for Hwy 4 but here one approaching grade decreases as the other one increases. Therefore the right side of this site has an approaching grade that increases causing the vehicle to already be slowing down.
- Regarding Case A- Intersections with no controls and the adjustment factor depending on the approach grade the calculation of the correct distance traveled by an approaching vehicle during perception-reaction and braking time as a function of the design speed of the roadway on which the intersection approach is located. The new values are the distances needed from approaching car to intersection.
- t is reaction time and it’s estimated to be at 2.5s. A is deceleration and its 11.2 ft/s Caluculated stopping distance is both of them combined and the design values is for the distances you need to take account into designing the plans The stopping distances needed on upgrades are shorter than on level roadways; those on downgrades are longer.
- Here we have the effects of skew. In the table we have the angle of the road to railroad tracks followed with the street width. When the street width is divided by the sin of the angle, you’re given the roadway width on the path of the crossing vehicle. From here you can calculate the extra time needed to cross the intersection. The equations are the square root of 2 times the W1 or W2 divided by the acceleration from a stop, which is 4.53 ft/s^2. From there you can subtract the time from 90 degrees to skewed crossing then add that values to the previous graph to state the actual time it will take to cross the intersection.
- This is the intersection sight distance for passenger cars with the effect of skewed values and approaching grade factors taken into account for both oncoming side of traffic at each site.
- For this part of the project, we wanted to see which way would be the best way to obtain coordinates for a certain site and build a 3D models with. Three different ways were considered: Lidar, Google Earth and Original Design.
- Here’s a few picture of the test site hwy 4 we visited.
- We initially decided to concentrate on Hwy 4 HRGC because of the image provided by google earth. As you can see here it looks like a tough crossing with different elevations approaching and departing the HRGC. We realized that at that location Google Earth last updated the imagery in 2009 therefore we did not notice that that site was already fixed until we visited it.
- Here is
- Regarding Part one For each test site, while taking into consideration of different approaching grade (from left and right) as well as the effect of the skewed crossing when necessary the following were obtained sight distance stopping distance braking distance Regarding Part two Google Earth The most efficient way to retrieve coordinates and build 3D models Original Design Plans Gave a more realistic and exact elevation, resulting in a more precise evaluation when discovering the vehicle’s dynamic profile after exported into CarSim