css pseudo class left arrow

.route-steps .route-contain::after {
  content: '';
  position: absolute;
  border: 4px solid transparent; // 重点
  border-left: 7px solid #7e838c; // 重点。。
  width: 0;
  right: -2px;
  top: 18px;
}
.route-steps .route-contain::before {
  content: '';
  position: absolute;
  border: 1px solid #7e838c;
  width: 4px;
  right: 9px;
  top: 21px;
}

effect: