Arduino. Why does my code work with a delay

Question

I have written a code that for some reason only works when I place a delay. It is supposed to be a traffic light

 int switchState = 0;

void setup() {
  pinMode(5, OUTPUT); // red light
  pinMode(4, OUTPUT); // yellow light
  pinMode(3, OUTPUT); // green light
  pinMode(2, INPUT);  // button, when pressed lights switch
  digitalWrite(5, HIGH);
}

void loop() {
  switchState = digitalRead(2);
  if(switchState == HIGH){  
    if(digitalRead(5) == HIGH) { // if the light is red
      digitalWrite(5, LOW);      // turn off red light
      digitalWrite(3, HIGH);     // turn on green light
      delay(500);                                   //It's this delay
    }
    else {                       // light is green
      digitalWrite(3, LOW);      // turn off green light
      digitalWrite(4, HIGH);     // turn on yellow light
      delay(500);                // yellow light turned on for a bit just like traffic light
      digitalWrite(4, LOW);      // turn off yellow light
      digitalWrite(5, HIGH);     // turn on red light
    }
  }
}  

I thought maybe it was because I held the button for "too long" and the loop ran twice and by adding a delay I have created enough time for me to release my finger, is this the case or is there something else going on?

EDIT: without the delay it will ALWAYS jump to the else statement, even when the red light is turned on

Answer 1

Looks like you are having some issues with Debouncing. more info

Buttons dont switch cleanly from open to closed, there is some jitter due to the mechanical nature.