Sight Distance Design
Comprehensive Sight Distance Calculator
Calculate Stopping (SSD), Decision (DSD), and Intersection (ISD) Sight Distances with automated grade and vehicle adjustments.
SSD Parameters
Stopping sight distance is the total of reaction distance and braking distance.
Default values: t = 2.5 s, a = 11.2 ft/s²
1.0 Design Speed
Design speed is a speed selected to determine the various geometric design features of a roadway.
Table 1. Design Speeds
Ref: Street Development Standards. City of Des Moines
| Road Type | Design Speed | Posted Speed |
|---|---|---|
| Principal Arterial | Posted + 5 | 35 - 45 |
| Minor Collector | Posted + 5 | 35 - 40 |
| Collector | Posted | 30 - 35 |
| Neighborhood Collector | Posted | 25 - 30 |
| Local Road | Posted (25) | 25 |
| Alley | Posted (20) | 20 |
Note 1: Not all Local Roads will be posted.
Note 2: Speed Limit Signs shall not be posted on Alleys.
Result
Total Stopping Sight Distance
0
ft
Distance Breakdown
0 ft
0 ft
Reaction Distance
0 ft
Braking Distance
0 ft
Formula: 1.47×V×t + V² / [30×((a/32.2) ± G)]
