Blog Archives

Stopping Sight Distance

The stopping sight distance (SSD) is the total distance you travel during the time you (a) react to apply brakes, (b) apply brakes and actually begin to decelerate, and (c) vehicle comes to a stop.

Reaction time from AASHTO () is 2.5 s.

Default deceleration rate from AASHTO is 11.2

The total distance traveled using these values on a straight path is:

Click here to continue reading

Vertical Curves

Vertical Curves are nice! I think they are easier to solve than Horizontal Curves because they are essentially parabola equations (which you should be very used to). This is the formula for vertical curves

is the elevation y at x horizontal distance into the curve from the start position

is the starting elevation at x = 0.

Click here to continue reading