It's great that you want to teach a developmentally disabled adult street safety! First, create realistic goals alongside either the student or their guardian. Then create an individualized lesson plan that is geared toward their abilities. You could even adapt an existing training plan to meet your student's needs. You may want to modify and use the tips, tricks, and games in the article above. Regularly check the process of your student by talking to them to find out how much they remember.