How to get car on top of the racetrack

i am working on a top down racing game, and currently i am trying to get the car to go on top of the racetrack. There are 2 cars, one is the computer's car (not finished) and the other is the user controlled car, however when i run the programme the user's car is behind the track, but still moves normally. I have tried a few different things, but the user's car never seems to get on top of the track. So i am mainly asking how to get the user's car on top of the track.

Thank you

import math
import random
from tkinter import *

import pygame

class Buttons:
#window
    def __init__(self, master):
        frame = Frame(master)
        frame.pack()

        self.quitButton = Button(frame, text="Race!", fg="red", command=frame.quit)
        self.quitButton.pack(side=LEFT)

root = Tk()
b = Buttons(root)
root.mainloop()

pygame.mixer.pre_init(44100,16,2,4096)
pygame.init()
screen = pygame.display.set_mode((1280, 800))
rect = screen.get_rect()
clock = pygame.time.Clock()

#music
pygame.mixer.music.load("Noteblock.mp3")
pygame.mixer.music.set_volume(0.5)
pygame.mixer.music.play(-1)

WHITE = pygame.Color('white')
# Load images globally and reuse them in your program.
# Also use the `.convert()` or `.convert_alpha()` methods after
# loading the images to improve the performance.

VEHICLE1 = pygame.Surface((40, 70), pygame.SRCALPHA)
VEHICLE1.fill((130, 180, 20))
#blitting car onto 'rectangle car'
VEHICLE1 = pygame.image.load("YellowLambo.png")
screen.blit(VEHICLE1,(0,0))
pygame.display.update()

VEHICLE2 = pygame.Surface((40, 70), pygame.SRCALPHA)
VEHICLE2.fill((200, 120, 20))
#blitting computer's car
VEHICLE2 = pygame.image.load("RedLambo.png")
screen.blit(VEHICLE2,(0,0))
pygame.display.update()

BACKGROUND = pygame.Surface((1280, 800))
BACKGROUND.fill((127, 69, 2))
BACKGROUND = pygame.image.load("track1.png").convert()
screen.blit(BACKGROUND,(0,0))
pygame.display.update()




class Entity(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)


class VehicleSprite(Entity):
    MAX_FORWARD_SPEED = 10
    MAX_REVERSE_SPEED = 2
    ACCELERATION = 0.05
    TURN_SPEED = 0.000000000001


    def __init__(self, image, position):
        Entity.__init__(self)
        self.src_image = image
        self.image = image
        self.rect = self.image.get_rect(center=position)
        self.position = pygame.math.Vector2(position)
        self.velocity = pygame.math.Vector2(0, 0)
        self.speed = self.direction = 0
        self.k_left = self.k_right = self.k_down = self.k_up = 0

    def update(self, time):
        # SIMULATION
        self.speed += self.k_up + self.k_down
        # To clamp the speed.
        self.speed = max(-self.MAX_REVERSE_SPEED,
                         min(self.speed, self.MAX_FORWARD_SPEED))

        # Degrees sprite is facing (direction)
        self.direction += (self.k_right + self.k_left)
        rad = math.radians(self.direction)
        self.velocity.x = -self.speed*math.sin(rad)
        self.velocity.y = -self.speed*math.cos(rad)
        self.position += self.velocity
        self.image = pygame.transform.rotate(self.src_image, self.direction)
        self.rect = self.image.get_rect(center=self.position)


class Background(pygame.sprite.Sprite):

    def __init__(self, image, location):
        pygame.sprite.Sprite.__init__(self)
        self.image = image
        self.rect = self.image.get_rect(topleft=location)


def game_loop():
    bike = VehicleSprite(VEHICLE1, rect.center)
    pygame.sprite.LayeredUpdates.move_to_front
    ball = VehicleSprite(VEHICLE2, rect.center)

    bike_group = pygame.sprite.Group(bike)
    ball_group = pygame.sprite.Group(ball)
    all_sprites = pygame.sprite.Group(bike_group, ball_group)
    background = Background(BACKGROUND, [0, 0])

    camera = pygame.math.Vector2(0, 0)
    done = False

    while not done:
        time = clock.tick(60)

        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                done = True
            elif event.type == pygame.KEYDOWN:
                # Bike Input (Player 1)
                if event.key == pygame.K_d:
                    bike.k_right = -5
                elif event.key == pygame.K_a:
                    bike.k_left = 5
                elif event.key == pygame.K_w:
                    bike.k_up = 2
                elif event.key == pygame.K_s:
                    bike.k_down = -2

                elif event.key == pygame.K_ESCAPE:
                    done = True
            elif event.type == pygame.KEYUP:
                if event.key == pygame.K_d:
                    bike.k_right = 0
                elif event.key == pygame.K_a:
                    bike.k_left = 0
                elif event.key == pygame.K_w:
                    bike.k_up = 0
                elif event.key == pygame.K_s:
                    bike.k_down = 0


        camera -= bike.velocity

        #screen.blit(background.image, background.rect)
        all_sprites.update(time)

        screen.fill(WHITE)



        for sprite in all_sprites:
            screen.blit(background.image, background.rect.topleft+camera)
            screen.blit(sprite.image, sprite.rect.topleft+camera)


        pygame.display.flip()


game_loop()
pygame.quit()

Solution

The problem lies in the for loop in which you blit the sprite images:

for sprite in all_sprites:
    screen.blit(background.image, background.rect.topleft+camera)
    screen.blit(sprite.image, sprite.rect.topleft+camera)

Here you blit the background and one of the sprites, then you blit the background again and the next sprite. So the background will be blit above the previous sprites in each iteration of the for loop.

Just blit the background once before the loop and then the sprites:

screen.fill(WHITE)
screen.blit(background.image, background.rect.topleft+camera)

for sprite in all_sprites:
    screen.blit(sprite.image, sprite.rect.topleft+camera)