Final answer:
The brake pipe pressure and straight air pipe pressure should be within the specified range for the brakes to function properly, and these pressures are measured in psi.
Step-by-step explanation:
Before moving a car, according to the updated instructions, the brake pipe pressure should be at a certain level, as should the straight air pipe pressure. These pressures ensure the braking system operates correctly and are measured in pounds per square inch (psi). It is vital to maintain the proper pressure levels for safety and efficiency. While the question does not specify the exact pressures needed, it's essential for these values to be within the specified range to ensure the brake system's reliability. For instance, when measuring tire pressure, if your gauge reads 34 psi, the absolute pressure is actually 48.7 psi when considering atmospheric pressure (14.7 psi).
The latest instructions state that before moving a car, the brake pipe pressure and straight air pipe pressure should be between 24 and 80 pounds per square inch (psi).
For example, if a tire gauge reads 34 psi, then the absolute pressure is 34 psi plus 14.7 psi (Patm in psi), or 48.7 psi. So, the brake pipe pressure and straight air pipe pressure should be within the range specified.