threads waiting unexpectedly not sure whats causing - c

Question

I'm wanting to stop traffic of opposing direction from crashing om the bridge. if the randomized get all cars heading east it works fine. It hangs on west bound traffic. im have a feeling that there's a better was to stop threads from colliding as im using so many sem_post() and sem_wait()
any suggestions or help welcome, still just learning threads so i expect to be missing something.
eventually i want randomised traffic from both direction as well as trucks that need the bridge all to them selves where as cars can share so long as the traffic flow is the same.
#include <signal.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <time.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <pthread.h>
#include <sys/sem.h>
#include <semaphore.h>
#define MAXCARS 5
#define MAXWAIT 10
#define CROSSINGTIME 2
int G_direction = 0;
int carNum;
int retVal=0, lower = 0, upper = 1;
int car_rid[MAXCARS];
pthread_t threads[MAXCARS];
sem_t direc_sem, car_E, car_W,bridge_sem;
const char* printRandoms() ///randomise the cars direction
{
int num = (rand() % (upper - lower + 1)) + lower;
if (num == 0){
//left headed west
return "west";
}else return "east";
//return num;
}
void *car(void *arg) {
int carNum = (int)(intptr_t)arg; //what car is it
const char* direction = printRandoms(); //random direction
printf(" car no %d is idling, planning to go %s \n",carNum, direction);// test print
sleep( rand() % MAXWAIT ); // wait a random amounnt of time
sem_wait(&direc_sem); //isolate the direction value
if(direction == "west"){
if (G_direction > 0){//g_direction -1 = one car headed west -2 two headed west
sem_wait(&car_E);//if traffic flow is in the wrong direction wait for the semaphore
}
G_direction--;//->> move ON the bridge
if (G_direction == -1){//if last car on bridge lock east bound traffic
sem_wait(&car_W);
}
}
sem_post(&direc_sem);
sem_wait(&direc_sem);//isolate the direction value
if(direction == "east"){
if (G_direction < 0){//g_direction 1 = one car headed east 2 two headed east
sem_wait(&car_W);//if traffic flow is in the wrong direction wait for the semaphore
}
G_direction++;//->> move ON the bridge
if (G_direction == 1){//if last car on bridge lock west bound traffic
sem_wait(&car_E);
}
}
sem_post(&direc_sem);
printf("car no %d goes ON the bridge heading %s \n", carNum,direction);
sleep(CROSSINGTIME);
printf("car no %d goes OFF the bridge heading %s \n", carNum, direction);
sem_wait(&direc_sem);//isolate the direction value
if(direction == "west"){
G_direction++;//->> move OFF the bridge
if (G_direction == 0){//if last car on bridge unlock other traffic
sem_post(&car_W);
}
}
sem_post(&direc_sem);
sem_wait(&direc_sem);//isolate the direction value
if(direction == "east"){
G_direction--;//->> move off the bridge
if (G_direction == 0){//if last car on bridge unlock other traffic
sem_post(&car_E);
}
}
sem_post(&direc_sem);
}
int main( void ){
sem_init(&direc_sem, 0, 1);
sem_init(&car_E, 0, 1);
sem_init(&bridge_sem, 0, 1);
for (int i = 0; i < MAXCARS; i++){
retVal = pthread_create(&threads[i], NULL,car ,(void *)(intptr_t)i);
if(retVal!=0){
printf("pthread_create failed in %d_th pass\n",i);
exit(EXIT_FAILURE);
}
}
for (int i = 0; i < MAXCARS; i++){
retVal = pthread_join(threads[i], NULL);
if(retVal!=0){
printf("pthread_join failed in %d_th pass\n",i);
exit(EXIT_FAILURE);
}
}
//sem_destroy(&carLock);
return 0;
}```