Reference tables
Stopping sight distance tables
Transcribed verbatim from the source manuals. Values are published as printed, including where a table disagrees with the equation in the same document — those cells are marked and explained rather than corrected.
Need a value between these, or on a grade the tables don't list?Use the calculator.
Level grade — all published columns
Source: TxDOT, Roadway Design Manual, §4.11.1 Table 4-23. Comparison columns from Caltrans HDM Table 201.1 and FHWA-SA-10-001 Table 2. All values in feet.
| Speed | Reaction | Braking | Calculated | TxDOT design | Caltrans | Mean driver | Dry roadway |
|---|---|---|---|---|---|---|---|
| 15 mph | 55.1 | 21.6 | 76.7 | 80 | 100 | 40 | 75 |
| 20 mph | 73.5 | 38.4 | 111.9 | 115 | 125 | 60 | 110 |
| 25 mph | 91.9 | 60.0 | 151.9 | 155 | 150 | 80 | 150 |
| 30 mph | 110.3 | 86.4 | 196.7 | 200 | 200 | 105 | 190 |
| 35 mph | 128.6 | 117.6 | 246.2 | 250 | 250 | 135 | 235 |
| 40 mph | 147.0 | 153.6 | 300.6 | 305 | 300 | 165 | 285 |
| 45 mph | 165.4 | 194.4 | 359.8 | 360 | 360 | 200 | 340 |
| 50 mph | 183.8 | 240.0 | 423.8 | 425 | 430 | 235 | 400 |
| 55 mph | 202.1 | 290.3 | 492.4 | 495 | 500 | 275 | 465 |
| 60 mph | 220.5 | 345.5 | 566.0 | 570 | 580 | 320 | 535 |
| 65 mph | 238.9 | 405.5 | 644.4 | 645 | 660 | 365 | 605 |
| 70 mph | 257.3 | 470.3 | 727.6 | 730 | 750 | 415 | 680 |
| 75 mph | 275.6 | 539.9 | 815.5 | 820 | 840 | 465 | 765 |
| 80 mph | 294.0 | 614.3 | 908.3 | 910 | 930 | 520 | 850 |
- Calculated is the raw equation output. TxDOT design is that value rounded up to the next 5 ft, and is the value used in design.
- Caltrans is California's independently adopted minimum. It is not a rounding of the calculated column, which is why it diverges above 45 mph.
- Mean driver is what an average driver actually needs (1.1 s reaction, 17.71 ft/s²). It is a comparison published by FHWA, not a design standard.
- Dry roadway is published by FHWA without a stated deceleration rate, so this site reproduces it as reference data only and does not compute it.
On grade
Source: TxDOT Table 4-24. All values in feet. Downgrades require more distance because gravity works against braking.
| Speed | 3% down | 6% down | 9% down | 3% up | 6% up | 9% up |
|---|---|---|---|---|---|---|
| 15 mph | 80 | 82 | 86* | 75 | 74 | 73 |
| 20 mph | 116 | 120 | 126 | 109 | 107 | 104 |
| 25 mph | 158 | 165 | 173 | 147 | 143 | 140 |
| 30 mph | 205 | 215 | 227 | 200* | 184 | 179 |
| 35 mph | 257 | 271 | 287 | 237 | 229 | 222 |
| 40 mph | 315 | 333 | 354 | 289 | 278 | 269 |
| 45 mph | 378 | 400 | 427 | 344 | 331 | 320 |
| 50 mph | 446 | 474 | 507 | 405 | 388 | 375 |
| 55 mph | 520 | 553 | 593 | 469 | 450 | 433 |
| 60 mph | 598 | 638 | 686 | 538 | 515 | 495 |
| 65 mph | 682 | 728 | 785 | 612 | 584 | 561 |
| 70 mph | 771 | 825 | 891 | 690 | 658 | 631 |
| 75 mph | 866 | 927 | 1003 | 772 | 736 | 704 |
| 80 mph | 965 | 1035 | 1121 | 859 | 817 | 782 |
These published cells disagree with the equation printed in the same section. The 30 mph 3% upgrade value of 200 ft should be 190 ft by the equation, a figure corroborated by WSDOT's AASHTO-derived table, and 200 ft breaks the monotonic ordering of its own row. See documented discrepancies for the full explanation.
Grades not shown in the table
The published grade table covers 3%, 6% and 9% only. Real alignments are rarely so convenient. The calculator applies the same equation continuously, so you can enter 4.5% or 7.2% and see the working rather than interpolating by hand.