  The statement ``no nonabelian simple group can be obtained from a nonsimple
group by adding one generator and one relator"
  1) is equivalent to the Kervaire--Laudenbach conjecture;
  2) becomes true under the additional assumption that the initial nonsimple
group is either finite or torsion-free.
  Key words: Kervaire--Laudenbach conjecture, relative presentations, simple
groups, car motion, cocar comotion.
  AMS MSC: 20E32, 20F05, 20F06.
