Highway robber

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A highway robber is any mechanism that can retrieve a signal from a spaceship lane while allowing spaceships on nearby lanes (even those a single lane away) to pass by unaffected. In practice the spaceship is generally a glider. The spaceship is removed from the lane in question, an output signal is generated elsewhere, and the highway robber returns to its original state. A competent highway robber does not affect spaceships even on the lane adjacent to the affected spaceship stream, except perhaps during the highway robber's recovery period.[1]

A stable highway robber with repeat time 878 was assembled by Chris Cain in 2015,[2] with an update by Entity Valkyrie in January 2019[3] to simplify the extraction of the output signal. A simpler highway robber with improved clearance and repeat time 876 was constructed by Louis-François Handfield in May 2020,[4] with subsequent improvements made by Goldtiger997.[5] The next version made use of the Bandersnatch to reduce the repeat time to 863 ticks.[6] On June 23, Goldtiger997 posted a larger staged recovery highway robber with a repeat time of 742 ticks.[7] A variant of this mechanism that allows for bounding box reduction was later assembled.[8]

x = 207, y = 247, rule = B3/S23 obo$b2o$bo9$13bo$14bo$12b3o153$134bo$133bobo$133bobo$127b2ob2obobob2o$ 126bobobobobobobo$122b2o2bo5bo3bo8bo$122bobob2o3b2o3b2o5b3o$124bo17bo$ 124b4o14b2o$122b2o3bo4bo$121bo2b3o4bobo$92b2o3b2o22b2obo6bobo$92b2o3b 2o25bo7bo$124b2o34b2o$161bo$85b2o74bob2o$86bo72bobobo$86bobo66b2o2b2o 2bo$87b2o66b2o6b3o$166bo19bo$165b2o20b2o$123bo62b2o$122bobo$122bobo$ 123bo$90b2o$91bo$88b3o$88bo35b2o$120bobo2bo$118b3ob3o18b2o$117bo3bo20b obo54bo$117b2o2bob2o17bo54bobo$122bobo16b2o55b2o2$103b2o92bo$103b2o91b obo$95b2o98bo2bo$96bo58b2o39b2o$93b3o59b2o$93bo67b2o$162bo$94bo64b3o$ 93bobo63bo$93bobo$91b3ob2o89b2o$90bo95b2o15b2o$91b3ob2o106bo$93bob2o 107b3o$196b2o8bo$103b2o91bo$103b2o7b2o83b3o$112bo86bo$110bobo$110b2o3$ 115bo$90b2o23b3o51bo$90b2o26bo50b3o$117b2o53bo$171b2o3$106bo$105bobo$ 105bobo$106bo20b2o$107b3o10b2o5bobo51b2o$109bo10b2o7bo44b2o5bobo$129b 2o43b2o7bo$183b2o$116bo$115bobob2o49bo$115bobobobo47bobob2o$112b2obobo bobo2bo44bobobobo$112bo2bo2b2ob4o41b2obobobobo2bo$114b2o4bo45bo2bo2b2o b4o$120bobo45b2o4bo$121b2o51bobo$175b2o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ THEME Book THUMBSIZE 2 WIDTH 840 HEIGHT 600 ZOOM 6 X 45 Y 85 AUTOSTART GPS 80 T 0 PAUSE 3 T 1669 PAUSE 2 LOOP 1670 ]]
A stable highway robber with 742-tick repeat time, allowing gliders to pass by on the same lane 47+ ticks after the activating glider. There are three possible glider outputs, but two of them are awkwardly close to other glider lanes.
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RLE: here Plaintext: here

A related but slightly different topic is to find a stable edgy eater with maximum clearance. The hypothetical device does not have to emit output signal(s), but it is expected to have a relatively small repeat time of less than 100. Existing methods such as tub-with-tail eater, sidesnagger and 7×9 eater do not qualify as solutions, because they cannot handle a glider immediately adjacent (1hd away) to the working input lane. Currently, whether such a pattern exists is still an open problem.


  1. Dave Greene (January 22, 2007). "Stable pseudo-Heisenburp device and other P1 wiring projects". Retrieved on December 2, 2018.
  2. Chris Cain (March 28, 2015). Re: The Hunting of the New Herschel Conduits (discussion thread) at the ConwayLife.com forums
  3. Entity Valkyrie (January 10, 2019). "RLE:Highwayrobber".
  4. Louis-François Handfield (May 25, 2020). Re: Highway robber challenge (discussion thread) at the ConwayLife.com forums
  5. Goldtiger997 (May 25, 2020). Re: Highway robber challenge (discussion thread) at the ConwayLife.com forums
  6. Goldtiger997 (June 5, 2020). Re: Highway robber challenge (discussion thread) at the ConwayLife.com forums
  7. Goldtiger997 (June 23, 2020). Re: Highway robber challenge (discussion thread) at the ConwayLife.com forums
  8. EvinZL (October 8, 2020). Re: Thread for your unsure discoveries (discussion thread) at the ConwayLife.com forums

External links