switch (FEAT_ROADVEHS, SELF, switch_e4_style, 
  max((date_of_last_service - random_bits*3)/365 - 2, build_year)
){  //style by build year
  0..1979:    spritegroup_d1_tram_04;
  1980..1984: spritegroup_d2_tram_04;
  1985..1989: spritegroup_d3_tram_04;
  1990..1997: spritegroup_d4_tram_04;
  1998..2004: spritegroup_d5_tram_04;
  2005..2014: spritegroup_d6_tram_04;
  default:    spritegroup_d7_tram_04;
}