To try to find the steepest paved road anywhere in Thailand, I ran the Garmin tracks of my Thailand rides from 2017 to 2023, 72,000 km, 2 million trackpoints, through GPS Visualizer and then a monster spreadsheet in Excel to identify the steepest 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 30, 40, 50, 60, and 70 km (16 specific distances) of each of the twenty routes I had taken. I had to use several filters, such as disallowing U-turns because otherwise the steepest routes often turned out to be up and down the same route, thus counting the steepest bits twice. And disallowing ferry crossings when I discovered that walking upstairs from the car deck to the roof with my Garmin Oregon in my pocket was computed as a steep hill in the sea! My ThinkPad took about four hours to process each of the twenty routes, by far the slowest Excel spreadsheets I ever made. Then I manually sorted the steepest of the sixteen distances for the twenty rides to get the steepest of the steepest.
I didn’t include my older tracks because the GPS system elevation accuracy was poor in years past, and anyway my later rides often included the most interesting parts of previous rides. Based on comparing multiple rides over the same routes, and based on comparison of my tracks with tracks GT Rider sent me, I estimate the accuracy of the steepness calculations to be within about half a percentage point.
Steepest means the highest time-averaged absolute value of the grades between trackpoints (measured over at least 3 meters while moving) along the route. I did a second analysis to identify the routes with the steepest grade divided by the lowest speed, time-averaged from trackpoint to trackpoint. “Grade/Speed” is of course subjective, being based on one rider’s speed on one day’s weather and road conditions, but it helps to compare two routes of similar steepness—a faster route usually takes less effort than a slower one (better surface, fewer hairpins, wider track).
These were the twenty rides the computer analyzed, by following the routes that I happened to take on each of these rides and segmenting them into all possible overlapping routes of the sixteen lengths mentioned above (tens of thousands of routes were calculated for each ride):
Here is a summary of the results, sorted together with longer routes that I selected manually for comparison:
The steepest roads I could find are the 5035 Elephant Pass, 4018 Big Dipper, 1345 Phu Anma, 5080 Mae Kampong, 1249 Nor Lae to Ang Khang, 4010 Ban Wiang, the Ko Pha Doh Road, 4009 West Segment, 1333 Phu Fa, 3037 Doi Pha Luang. The most intense roads (Grade/Speed) I could find are Ko Pha Doh Road, 1345 Phu Anma, 3037 Doi Pha Luang, 5035 Elephant Pass, 5080 Mae Kampong, 4010 Ban Wiang, 4018 Big Dipper, 4009 West Segment.
Of course, long and short rides can’t be compared with each other but only with other rides of similar length, like marathons and sprints. Almost any ride can be made steep, if you make it short enough.
If anyone has a correction or addition, please PM me a recent GPS track (coordinates, elevations, and timestamps) that should be on this list. I’ll gladly run it through the analyzer and add it. It doesn’t take long.
Here is the same list as a text file, in case anyone wants to cut and past the coordinates into Google Maps to see the (approximate) routes.
19.192119,098.063456 to 19.219267,098.031105 > 5035 Elephant Pass 06 km
19.871104,100.356972 to 19.880315,100.307487 > 4018 Big Dipper 07 km
19.463951,100.511164 to 19.461167,100.530289 > 1345 Phu Anma 06 km
18.863648,099.356208 to 18.840115,099.374842 > 5080 Mae Kampong
19.850795,099.067989 to 19.869779,099.053002 > 1249 Nor Lae to Ang Khang
18.197692,100.435386 to 18.183008,100.487318 > 4010 Ban Wiang
19.884056,100.292859 to 19.860756,100.367548 > 4018 Big Dipper 11 km
17.236142,098.341312 to 17.280666,098.372167 > Ko Pha Doh Road 14 km
19.208824,098.076024 to 19.244495,097.996111 > 5035 Elephant Pass 20 km
19.007785,097.978359 to 18.997637,098.047005 > 4009 West Segment
18.970210,101.105007 to 18.989009,101.191410 > 1333 Phu Fa
20.079278,099.185297 to 20.059926,099.169558 > 3037 Doi Pha Luang 05 km
17.288621,098.356489 to 17.296685,098.393055 > Ko Pha Doh Road 07 km
17.210460,098.331498 to 17.355516,098.477927 > Ko Pha Doh Road to Mae Tuen
20.062013,099.208988 to 20.041619,099.163970 > 3037 Doi Pha Luang 12 km
19.495665,100.458612 to 19.453175,100.528421 > 1345 Phu Anma 14 km
18.1578120,100.36719 to 18.181743,100.490415 > 1024, 1342, 4010 Nam Gon
19.790236,100.341187 to 19.784439,100.401651 > Lao U (Rom Pho Sai) Road
17.9660770,097.92928 to 17.979350,097.977980 > 3004 Eng Neo Microwave
20.0020440,100.48522 to 19.947709,100.510123 > 4029 Singapore Road
17.088599,098.513192 to 17.151985,098.475324 > 3054 Steepest Segment
19.095506,100.412406 to 19.078973,100.499420 > 4330 Doi Pha Chi Santisuk
16.3697130,099.01101 to 16.229190,098.928276 > 1090 to Umphang 40 km
19.181050,100.984336 to 19.148827,101.155546 > 1256 Doi Phu Kha
16.460658,098.909929 to 16.229190,098.928276 > 1090 to Umphang 90 km
16.876672,101.171961 to 16.896666,101.105754 > 2331 Phu Thap Boek
19.988136,100.467104 to 19.933865,100.508378 > 4029 Doi Pha Tang Road
17.018803,098.523733 to 17.404135,098.456724 > 3054 to Mae Tuen
19.806480,099.132890 to 19.940880,099.042265 > 1249 to Ban Nor Lae
20.180510,099.771193 to 20.104088,099.615590 > 1130, 1234 Mae Salong
19.851354,100.380501 to 19.850039,100.438944 > 1155 to Phu Chi Fa
19.008597,097.974443 to 18.827524,098.036903 > 4009 Past Sunflowers
20.311914,099.820177 to 20.293884,099.769852 > 1334 Pha Bur
18.229392,100.411231 to 18.179997,100.657349 > 4010 to Na Muen
16.724886,098.595953 to 16.018195,098.862176 > 1090 to Umphang 163 km
19.481578,097.963383 to 19.587518,097.943319 > 4001 Ban Rak Thai Road
19.279550,098.604750 to 19.558010,098.637140 > 4030 to Wiang Haeng
18.376637,097.942922 to 18.355165,098.133765 > 4006 Mae La Noi to La Up
20.434787,099.877948 to 20.180518,099.771209 > 1149, 1338 Doi Tung
18.317150,100.611485 to 18.345283,100.443168 > 1216 to Wang Pung
19.0209560,098.85334 to 19.017451,098.763295 > Buddha Footprint Temple
18.909811,100.950202 to 18.986114,101.056527 > 1257 Khun Nam Nae
19.569811,100.926206 to 19.518395,101.222232 > 1081, 101 Khun Nan
19.136400,100.790745 to 19.115163,100.649514 > 4022 to Sop Khun
20.166211,099.711967 to 20.330070,099.634890 > 4052 Yaek,Thoed Thai,Mae Moh
19.413847,098.915385 to 19.384120,098.717131 > 3024 Mueang Khong
18.490877,098.672954 to 18.589250,098.487274 > 1009 to Doi Inthanon
18.6732420,100.99196 to 18.747971,101.195998 > 1168 to Viewpoint
19.134115,098.704083 to 19.284313,098.485364 > 1095 to Hua Kaeo
19.359495,100.702797 to 19.406461,100.397685 > 1148 Past Biker Cafe
19.506664,098.957969 to 19.681574,098.626384 > 1322 Doi Mae Salong
13.850862,100.639559 to 14.023118,099.532149 > 346 to Kanchanaburi