My OSM selection script:

area[admin_level=2][name="Česko"];
way[highway][junction=roundabout](area) -> .all;
make counter num = 0 -> .count;
foreach.all {
  if (! lrs_in(u(id()), visited_ids.set(t['ids'])))
  {
    complete {
      node(w);
      way.all(bn);
    }
    make visited
      ids = lrs_union(set(id()), visited_ids.set(t['ids']))
      -> .visited_ids;
    .count convert counter num = t['num'] + 1 -> .count;
    make stat circ=sum(length()),wids=set(id());
    out;
  }
}
.count out;

Warning: Not all of these are actual roundabouts, unless I manually checked them (see icon)! The links point to one of consecutive line segments that have the junction=roundabout property, and the number is their total length in meters!

Part 2 ► | Part 3 ►►

1243,323 m C01P04 //TOP 00 Ostrava-Přívoz [D1]×[I/56]
1236,993 m C01b //no C01 sign Úsilné [D3]×[I/34]
1199,566 m C01P04 //TOP 01 Ostrava-Svinov [D1]×[I/11]
1110,363 m A15 //[highway=construction]
937,861 m A15 //[highway=construction]
859,544 m A15 //[highway=construction] dammit, why are we even building new highways???
730,454 m C01P04 //TOP 02 Ostrava hl.n. [I/56]×[II/647]; bonus points for an unofficial cul-de-sac roundabout inside
717,208 m C01P04 //TOP 03 Hradec Králové-Plotiště n/L [D11]×[I/35]×[I/11]
656,361 m C01P04 //TOP 04 Opatovice n/L [D35]×[I/37]; largest you’ll find described as “largest” in media
632,573 m C01P04 //MANUAL: area[name="Náměšť na Hané"]; way[name="Hrad"](area) -> .all; zámek Náměšť na Hané 🏰
578,223 m A34 //[highway=proposed]if that’s what it takes, I’m proposing to encircle the entire country in high speed rail
562,525 m C01P04 //TOP 06 Opava-Malé Hoštice [I/11]×[I/55]
508,368 m C01P04 //TOP 07 Brno, Slovanské nám.; town rectangle with park
487,721 m C01P04 //TOP 08 České Budějovice, nám. Přemysla Otakara II.; literal, barren town square
450,956 m C01P04 //TOP 09 Ostrava-Mariánské Hory [II/470]×[II/647]
445,589 m C01P04 //TOP 10 Plzeň-Jižní předměstí [I/27]×Folmavská
435,249 m C01P04 //TOP 11 Plzeň-Nová Hospoda [I/26]×Folmavská
424,798 m ) C01P04 //TOP 12 Časy [D35]×[I/36]
406,55 m C01 //MANUAL: area[name="Havířov"]; way[junction=circular](area) -> .all; Rondel Havířov [I/11]×[II/475]
401,29 m C01P04 //TOP 14 České Budějovice-Světlík [I/34]×[II/634]
393,052 m A15 //[highway=construction]
369,076 m A34 //[highway=proposed]
352,274 m C01P04 //TOP 15 Frýdek-Místek-Bahno [D48]×[I/56]
350,704 m C01P04 //TOP 16 Uničov, Masarykovo nám., town trapezoid
349,701 m C01P04 //TOP 17 Rumburk-Pražská [I/9]×[II/263]
340,176 m C01P04C01 2 regular ones, OSM error
330,095 m C01P04 //TOP 18 Modřice-Decathlon [D3]×[II/152]
321,686 m C01P04 //TOP 19 Praha-Chodov, Litochlebské nám.
320,525 m C01P04 //TOP 20 Praha-Chodov, Horní Roztyly-Westfield
319,749 m
318,428 m
316,409 m
314,548 m
310,452 m
302,83 m
302,676 m
301,835 m
301,502 m
299,473 m
290,541 m C01P04 Praha-Dejvice, Vítězné náměstí (Kulaťák) - Google thinks this is the biggest one, lol
288,75 m
288,493 m
288,248 m
287,169 m A15 //[highway=construction] traffic peanut! 🥜 First in country? Jivno [I/34]×[II/634]
285,816 m
285,358 m
280,815 m
277,924 m
274,537 m
267,542 m
265,443 m
256,774 m
254,253 m
253,741 m
253,49 m
252,515 m
252,452 m
249,304 m
248,891 m
245,692 m
238,742 m
236,662 m
234,46 m
233,957 m
233,882 m
232,679 m
228,321 m
222,969 m
222,217 m
221,342 m
220,291 m
219,886 m
218,16 m
218,086 m
217,452 m
211,977 m
210,808 m
209,791 m
209,54 m
207,088 m
206,672 m
206,042 m
205,371 m
202,178 m
201,382 m
200,672 m
200,051 m
199,431 m
199,012 m
196,548 m
196,431 m
196,232 m
193,53 m
193,339 m
192,183 m
192,046 m
191,663 m
191,381 m
190,061 m
188,097 m
187,915 m
187,678 m
186,76 m
184,929 m
182,863 m
182,481 m
179,572 m
177,071 m
176,836 m
176,829 m
176,691 m
176,429 m
174,812 m
173,465 m
172,491 m
172,311 m
172,142 m
170,633 m
168,694 m
168,603 m
168,568 m
168,386 m
168,3 m
168,072 m
167,724 m
167,494 m
167,065 m
166,348 m
165,997 m
165,993 m
165,739 m
163,63 m
163,518 m
163,472 m
163,395 m
163,308 m
162,533 m
162,121 m
161,734 m
161,001 m
159,855 m
159,034 m
158,249 m
158,047 m
156,868 m
156,83 m
156,749 m
156,482 m
156,399 m
155,188 m
155,106 m
154,621 m
154,488 m
154,431 m
154,058 m
153,918 m
152,583 m
152,214 m
152,208 m
151,91 m
151,686 m
151,138 m
150,5 m
149,75 m
148,329 m
148,071 m
146,826 m
146,436 m
146,391 m
145,823 m
145,793 m
145,665 m
145,141 m
145,141 m
144,539 m
143,951 m
143,453 m
143,45 m
143,234 m
143,143 m
142,973 m
142,435 m
142,384 m
142,373 m
142,323 m
142,319 m
142,138 m
141,965 m
141,843 m
141,755 m
141,732 m
141,408 m
140,944 m
140,943 m
140,894 m
140,502 m
140,287 m
140,233 m
140,175 m
140,046 m
140,044 m
140,013 m
139,954 m
139,916 m
139,825 m
139,824 m
139,448 m
139,288 m
139,16 m
139,012 m
138,867 m
138,766 m
138,471 m
138,47 m
138,461 m
138,224 m
138,185 m
138,15 m
138,078 m
138,013 m
137,992 m
137,577 m
137,489 m
137,294 m
137,252 m
137,186 m
137,071 m
136,997 m
136,97 m
136,819 m
136,688 m
136,553 m
136,125 m
135,93 m
135,675 m
135,355 m
135,124 m
134,797 m
134,477 m
134,105 m
134,008 m
133,979 m
133,808 m
133,638 m
133,529 m
133,424 m
133,308 m
133,248 m
133,171 m
133,022 m
133,02 m
132,829 m
132,671 m
132,373 m
131,446 m
131,089 m
130,939 m
130,908 m
130,847 m
130,844 m
130,838 m
130,766 m
130,489 m
130,338 m
130,257 m
130,239 m
130,127 m
129,778 m
129,538 m
129,232 m
129,198 m
129,052 m
128,966 m
128,569 m
128,45 m
128,369 m
128,368 m
128,238 m
127,69 m
127,595 m
127,563 m
127,521 m
127,515 m
127,505 m
127,148 m
127,111 m
126,651 m
126,555 m
126,418 m
126,198 m
126,127 m
125,918 m
125,742 m
125,738 m
125,449 m
125,424 m
125,366 m
125,278 m
124,898 m
124,645 m
124,245 m
124,15 m
124,126 m
124,072 m
124,031 m
123,78 m
123,642 m
123,639 m
123,617 m
123,615 m
123,577 m
123,48 m
123,457 m
123,443 m
123,384 m
122,913 m
122,739 m
122,471 m
122,468 m
122,452 m
122,135 m
122,08 m
121,834 m
121,744 m
121,676 m
121,592 m
121,557 m
121,494 m
120,924 m
120,744 m
120,645 m
120,612 m
120,598 m
120,402 m
120,21 m
120,184 m
120,123 m
120,105 m
120,022 m
119,883 m
119,803 m
119,799 m
119,77 m
119,757 m
119,7 m
119,458 m
119,356 m
119,242 m
119,235 m
119,093 m
118,816 m
118,715 m
118,571 m
118,433 m
118,287 m
117,832 m
117,744 m
117,557 m
117,45 m
117,128 m
116,779 m
116,724 m
116,37 m
116,181 m
116,076 m
116,015 m
115,952 m
115,556 m
115,498 m
115,258 m
115,223 m
115,165 m
115,157 m
115,154 m
115,035 m
114,775 m
114,717 m
114,41 m
114,186 m
113,678 m
113,514 m
113,459 m
113,458 m
113,443 m
113,386 m
113,154 m
113,131 m
113,062 m
112,932 m
112,92 m
112,865 m
112,655 m
112,547 m
112,25 m
112,194 m
112,179 m
112,062 m
111,921 m
111,9 m
111,874 m
111,732 m
111,696 m
111,69 m
111,636 m
111,539 m
111,47 m
111,389 m
111,386 m
111,227 m
111,214 m
111,136 m
111,102 m
110,958 m
110,831 m
110,671 m
110,666 m
110,615 m
110,367 m
110,36 m
110,343 m
110,336 m
110,237 m
110,095 m
110,014 m
109,998 m
109,991 m
109,982 m
109,979 m
109,935 m
109,927 m
109,749 m
109,716 m
109,687 m
109,662 m
109,651 m
109,645 m
109,569 m
109,52 m
109,493 m
109,431 m
109,4 m
109,398 m
109,377 m
109,339 m
109,335 m
109,244 m
109,12 m
109,079 m
109,061 m
109,028 m
108,842 m
108,811 m
108,719 m
108,71 m
108,651 m
108,635 m
108,573 m
108,543 m
108,502 m
108,451 m
108,433 m
108,425 m
108,413 m
108,336 m
108,288 m
108,278 m
108,215 m
108,201 m
108,123 m
108,045 m
108,038 m
108,019 m
107,997 m
107,995 m
107,96 m
107,958 m
107,951 m
107,946 m
107,94 m
107,857 m
107,778 m
107,767 m
107,761 m
107,602 m
107,53 m
107,5 m
107,318 m
107,266 m
107,265 m
107,234 m
107,168 m
107,114 m
107,068 m
107,032 m
107,03 m
106,895 m
106,865 m
106,863 m
106,861 m
106,856 m
106,807 m
106,792 m
106,773 m
106,687 m
106,674 m
106,67 m
106,661 m
106,633 m
106,606 m
106,567 m
106,499 m
106,432 m
106,345 m
106,31 m
106,299 m
106,29 m
106,243 m
106,136 m
106,128 m
106,126 m
106,047 m
106,043 m
106,003 m
106 m
105,959 m
105,923 m
105,902 m
105,819 m
105,677 m
105,669 m
105,657 m
105,64 m
105,604 m
105,485 m
105,479 m
105,444 m
105,308 m
105,229 m
105,139 m
105,134 m
105,128 m
105,064 m
104,948 m
104,894 m
104,89 m
104,83 m
104,79 m
104,78 m
104,772 m
104,744 m
104,709 m
104,694 m
104,607 m
104,591 m
104,494 m
104,441 m
104,34 m
104,289 m
104,271 m
104,175 m
104,172 m
104,159 m
104,142 m
104,142 m
104,141 m
104,139 m
104,122 m
104,041 m
104,01 m
103,949 m
103,942 m
103,916 m
103,874 m
103,79 m
103,781 m
103,618 m
103,563 m
103,562 m
103,495 m
103,445 m
103,234 m
103,165 m
103,106 m
103,029 m
103,002 m
102,881 m
102,809 m
102,752 m
102,735 m
102,726 m
102,677 m
102,603 m
102,551 m
102,526 m
102,501 m
102,492 m
102,455 m
102,382 m
102,354 m
102,323 m
102,322 m
102,222 m
102,121 m
102,07 m
101,999 m
101,978 m
101,944 m
101,913 m
101,799 m
101,77 m
101,754 m
101,748 m
101,564 m
101,548 m
101,528 m
101,478 m
101,38 m
101,348 m
101,311 m
101,268 m
101,256 m
101,25 m
101,212 m
101,206 m
101,166 m
101,101 m
101,096 m
101,048 m
101,025 m
100,98 m
100,859 m
100,803 m
100,757 m
100,751 m
100,725 m
100,711 m
100,633 m
100,621 m
100,603 m
100,594 m
100,558 m
100,522 m
100,518 m
100,514 m
100,471 m
100,425 m
100,42 m
100,393 m
100,378 m
100,375 m
100,373 m
100,366 m
100,295 m
100,261 m
100,233 m
100,217 m
100,185 m
100,178 m
100,126 m

Whether a crossroad in the Czech Republic is officially, actually, really, undoubtedly, a roundabout, is decided SOLELY based on the presence/absence of the C01 sign C01, not OSM data! I am not responsible for your accidents.

    • ChaoticNeutralCzech@lemmy.mlOP
      link
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      2
      ·
      edit-2
      3 months ago

      Unsurprisingly, it only works because most of the script was stolen from this blog post on roundabout counting (For the record, it identified 2097 roundabouts; the OSM “roundabout” definition differs from what the C01 sign “Kruhový objezd” signifies - the latter does not imply right-of-way of vehicles at the intersection.) I don’t really know much about the OSM3S language or whatever it is called, it is absolutely atrocious IMO. I wanted to pick one way segment of each roundabout and print its geolocation coordinates but I spent over an hour trying to figure out how to isolate one (any: first, last, shortest, lowest ID, whatever!) of the segments and ultimately failed. Eventually, I just had the script print all way IDs (not too many to crash, thankfully) and parsed the text to create Markdown links to OSM from the IDs (hence posting it here, it’s the first Markdown renderer that came to mind). Then, I used Redirector rule https://www.openstreetmap.org/way/.*/([\.0-9]+)/([\.0-9]+)https://en.mapy.cz/zakladni?x=$2&y=$1&z=17&ovl=8 to get Czech street view of the area to look for the traffic signs, and describe the roundabout locations in plain language. At “normal” circumference of 50 m to 300 m, it is unlikely we’ll have many false ones unless they are planned/under construction, which can be filtered automatically. There are questionable ones such as in Havířov, where C01 signs are present but the “roundabout” stops for traffic lights, or cul-de-sacs ending in “kruhový objezd” as per C01 signage, but where the circling vehicles don’t have priority because of no P04 signs which otherwise almost always accompany C01s.

      FYI, the smallest one is on a kindergarten’s traffic playground. Not counting zero-length nodes tagged [junction=roundabout] like this another kindergarten one or this pathway around a village pump that has no practical or legal implication of one-way “traffic”, the 30 smallest ones are 31,859 m, 31,793 m, 31,457 m, 31,350 m, 31,265 m, 31,203 m, 31,197 m, 30,749 m, 30,480 m, 29,851 m, 29,257 m, 29,158 m, 28,968 m, 28,335 m, 27,552 m, 27,445 m, 26,990 m, 25,258 m, 24,541 m, 24,465 m, 24,014 m, 21,097 m, 20,686 m, 19,804 m, 18,512 m, 18,244 m, 18,194 m, 16,500 m, 16,005 m, 13,394 m, 11,884 m