user58492: The code is made to sense were an object is and send out 
int const trigPin = 10;
int const echoPin = 9;
int const buzzPin = 1;
int const LED1 = 2;
int const LED2 = 3;
int const LED3 = 4;
void setup()
{
pinMode(trigPin, OUTPUT); 
pinMode(echoPin, INPUT); 
pinMode(buzzPin, OUTPUT); 
pinMode(LED1, OUTPUT);
pinMode(LED2, OUTPUT);
pinMode(LED3, OUTPUT);
}
void loop()
{
int duration, distance;
digitalWrite(trigPin, HIGH);
delay(1);
digitalWrite(trigPin, LOW);
duration = pulseIn(echoPin, HIGH);
//                                      Go
distance = (duration/2) / 29.1;
if (distance <= 1000 && distance >=0) { 
digitalWrite(LED1, HIGH);
} else {
digitalWrite(buzzPin, LOW);
digitalWrite(LED1, LOW);
}
delay(60);
}
//                                      SLOW
if (distance <= 50 && distance >=0) { 
digitalWrite(LED2, HIGH);
} else {
digitalWrite(buzzPin, LOW);
digitalWrite(LED2, LOW);
}
delay(60);
}
//                                      STOP
if (distance <= 50 && distance >=0) { 
digitalWrite(buzzPin, HIGH);
digitalWrite(LED3, HIGH);
} else {
digitalWrite(buzzPin, LOW);
digitalWrite(LED3, LOW);
}
delay(60);
}


user48341: Try adding in some serial output at important code-parts. If you see that these are getting printed you can be sure that the code gets executed until that point. If it doesn't get executed it could also be a problem with the wiring so be sure to check that everythign is set up properly. 
At this part:
...
void loop()
{
int duration, distance;
digitalWrite(trigPin, HIGH);
delay(1);
digitalWrite(trigPin, LOW);
duration = pulseIn(echoPin, HIGH);
//                                      Go
distance = (duration/2) / 29.1;
...

You are trying to divide an integer (wich can only hold whole numbers) with a real number. Please make sure to use a data type wich can hold more fine-grained results like double or float. 
To set up a serial interface you have to add Serial.begin(9600) to you code in the setup() function. Then when you write Serial.println("Your debugging message here") it should be visible in the serial monitor after compiling. (Arduino IDE->Tools->Serial Monitor)

58492: <p>The code is made to sense were an object is and send out </p>

<pre><code>int const trigPin = 10;
int const echoPin = 9;
int const buzzPin = 1;
int const LED1 = 2;
int const LED2 = 3;
int const LED3 = 4;
void setup()
{
pinMode(trigPin, OUTPUT); 
pinMode(echoPin, INPUT); 
pinMode(buzzPin, OUTPUT); 
pinMode(LED1, OUTPUT);
pinMode(LED2, OUTPUT);
pinMode(LED3, OUTPUT);
}
void loop()
{
int duration, distance;
digitalWrite(trigPin, HIGH);
delay(1);
digitalWrite(trigPin, LOW);
duration = pulseIn(echoPin, HIGH);
//                                      Go
distance = (duration/2) / 29.1;
if (distance &lt;= 1000 &amp;&amp; distance &gt;=0) { 
digitalWrite(LED1, HIGH);
} else {
digitalWrite(buzzPin, LOW);
digitalWrite(LED1, LOW);
}
delay(60);
}
//                                      SLOW
if (distance &lt;= 50 &amp;&amp; distance &gt;=0) { 
digitalWrite(LED2, HIGH);
} else {
digitalWrite(buzzPin, LOW);
digitalWrite(LED2, LOW);
}
delay(60);
}
//                                      STOP
if (distance &lt;= 50 &amp;&amp; distance &gt;=0) { 
digitalWrite(buzzPin, HIGH);
digitalWrite(LED3, HIGH);
} else {
digitalWrite(buzzPin, LOW);
digitalWrite(LED3, LOW);
}
delay(60);
}
</code></pre>
 48341: <p>Try adding in some serial output at important code-parts. If you see that these are getting printed you can be sure that the code gets executed until that point. If it doesn't get executed it could also be a problem with the wiring so be sure to check that everythign is set up properly. </p>

<p>At this part:</p>

<pre><code>...
void loop()
{
int duration, distance;
digitalWrite(trigPin, HIGH);
delay(1);
digitalWrite(trigPin, LOW);
duration = pulseIn(echoPin, HIGH);
//                                      Go
distance = (duration/2) / 29.1;
...
</code></pre>

<p>You are trying to divide an integer (wich can only hold whole numbers) with a real number. Please make sure to use a data type wich can hold more fine-grained results like double or float. </p>

<p>To set up a serial interface you have to add <strong>Serial.begin(9600)</strong> to you code in the setup() function. Then when you write <strong>Serial.println("Your debugging message here")</strong> it should be visible in the serial monitor after compiling. (Arduino IDE->Tools->Serial Monitor)</p>
