How to download table from website using rvest

I want to download a station departure map of a website. However, I'm not really getting anywhere with web scraping the table. Can someone help me?

library(rvest)
library(tidyverse)

link <- "https://reiseauskunft.bahn.de/bin/bhftafel.exe/dn?ld=4391&protocol=https:&rt=1&"

html <- read_html(link)

If you now open that link in a new browser tab or window, you will also end up with just a search form and no timetable. It's same for rvest, it must first fill and submit a form, content with a timetable is a response to the search form:

library(rvest)

link <- "https://reiseauskunft.bahn.de/bin/bhftafel.exe/dn?ld=4391&protocol=https:&rt=1&"
html <- read_html(link)

html %>% 
  # find form
  html_element("#sqQueryForm") %>% 
  html_form() %>% 
  # fill Bahnhof / Haltestelle & submit
  html_form_set(input = "Erfurt Hbf") %>% 
  html_form_submit() %>% 
  # parse response
  read_html() %>% 
  html_element("table.result") %>% 
  html_table()
#> # A tibble: 84 × 6
#>    Zeit   ``                 Zug          Richtung / Unterwegs…¹ Gleis Aktuelles
#>    <chr>  <chr>              <chr>        <chr>                  <chr> <chr>    
#>  1 früher ""                 ""           ""                     ""    ""       
#>  2 17:26  ""                 "ICE  504"   "München Hbf\n\n\n\nM… "9"   "Änderun…
#>  3 17:28  ""                 "ICE 1171"   "Berlin Hbf (tief)\n\… "2"   "18:29,G…
#>  4 18:09  ""                 "ICE 1002"   "München Hbf\n\n\n\nM… "1"   "18:44,G…
#>  5 18:22  "aktuelle Uhrzeit" "aktuelle U… ""                     ""    ""       
#>  6 18:22  ""                 "STR    2"   "P+R-Platz Messe, Erf… "-\n… "18:22"  
#>  7 18:23  ""                 "STR    6"   "Steigerstraße, Erfur… "-\n… "18:23"  
#>  8 18:23  ""                 "Bus  220"   "Busbahnhof, Sömmerda… "-\n… "18:23"  
#>  9 18:24  ""                 "ICE  704"   "München Hbf\n\n\n\nM… "9"   "18:25"  
#> 10 18:24  ""                 "STR    2"   "Wiesenhügel, Erfurt\… "-\n… "18:24"  
#> # ℹ 74 more rows
#> # ℹ abbreviated name: ¹​`Richtung / Unterwegshaltestellen`

^{Created on 2023-07-31 with reprex v2.0.2}

The form values are transmitted as a POST request wich means that the values are not transmitted as part of the URL path, but rather in an encapsulated payload. Interestingly though when we click on "spaeter" a GET request is used, and we can see a URL with the parameters. We can use that URL to access the time table:

library(rvest)
library(tidyverse)

link <- "https://reiseauskunft.bahn.de/bin/bhftafel.exe/dn?ld=4391&country=DEU&protocol=https:&rt=1&input=Erfurt%20Hbf%238010101&boardType=dep&time=18:23%2B60&productsFilter=11111&&&date=31.07.23&&selectDate=&maxJourneys=&start=yes"

response_html <- read_html(link)

response_html |> 
  html_table() |> 
  pluck(2)
#> # A tibble: 24 × 6
#>    Zeit   ``                 Zug          Richtung / Unterwegs…¹ Gleis Aktuelles
#>    <chr>  <chr>              <chr>        <chr>                  <chr> <chr>    
#>  1 früher ""                 ""           ""                     ""    ""       
#>  2 18:44  "aktuelle Uhrzeit" "aktuelle U… ""                     ""    ""       
#>  3 19:23  ""                 "FLX 1246"   "Berlin Hbf (tief)\n\… "10"  "19:34"  
#>  4 19:28  ""                 "ICE  502"   "Hamburg-Altona\n\n\n… "9"   "19:39,G…
#>  5 19:30  ""                 "ICE  273"   "Karlsruhe Hbf\n\n\n\… "2"   "Änderun…
#>  6 19:32  ""                 "ICE  801"   "München Hbf\n\n\n\nE… "1"   "19:32"  
#>  7 19:35  ""                 "RE     7(3… "Würzburg Hbf\n\n\n\n… "3a"  ""       
#>  8 19:36  ""                 "RE    17(7… "Naumburg(Saale)Hbf\n… "4"   ""       
#>  9 19:38  ""                 "RB    23(8… "Saalfeld(Saale)\n\n\… "6"   "19:38"  
#> 10 19:38  ""                 "RB    46(8… "Ilmenau\n\n\n\nErfur… "6"   "19:38"  
#> # ℹ 14 more rows
#> # ℹ abbreviated name: ¹​`Richtung / Unterwegshaltestellen`

Another option would be to use the Fahrplan API. You can request an API Key and there is an R package to interact with the Farhplan API: openbahn.