Stopping & Passing Sight Distance Calc
Estimate stopping distance and view separate tabulated ERA references for level-road SSD, minimum PSD and vertical curve K.
Compare the effect of grade and reaction time with the dry paved-road reference values.
- •ERA Geometric Design Manual 2013, §7.2 and Tables 7-2, 9-1 and 9-3
- •Highway Safety Auditors
- •Geometric Design Engineers
SSD = 0.278 Vt + V² / [254(f + g/100)]V in km/h, t in seconds, f is dimensionless, and g is signed grade in percent.Use these outputs for preliminary checks. They do not constitute official engineering approval. Verify the inputs, method and results against the project criteria before using them for design or construction.
Stopping & Passing Sight Distance Calculator
Estimate stopping sight distance for a dry paved road and compare ERA 2013 tabulated stopping, passing and vertical curve values.
Report Metadata
ERA 2013 dry paved-road screen. AASHTO and AACRA calculations require separately verified criteria.
Geometric Design Parameters
Distance & Sight Line Component Breakdown
Tabulated vertical curve K (m/%)
STOPPING & PASSING SIGHT DISTANCE CALCULATION REPORT
Reference Basis: Selected geometric design criteria (Based on selected ERA 2013 criteria)
| Project Name: | [Insert Project Title] | Date / Time: | |
| Section / Location: | [Insert Section Details] | Design Standard: | ERA Geometric Manual 2013 |
| Evaluated By: | User-entered project information | Design Speed: | 80 km/h |
1. Sight Distance & Component Breakdown
| Grade (%) | Perception Dist | Braking Dist | Calculated SSD | Passing Dist (PSD) |
|---|---|---|---|---|
| -4% | 55.60 m | 95.08 m | 150.68 m | 545 m |
ERA Table 7-2 level SSD: 140 m. Table 9-1 crest K (0.20 m object): 45 m/%. Table 9-3 sag comfort K: 16 m/%. Project-specific alignment and visibility checks are separate.
ENGINEERING VERIFICATION: Review and verify the result against project-specific data, governing specifications and professional engineering judgment before final use.
Engineering Guidance & Concept Notes (ERA 2013 Manual)
1. Downgrade Corrections
A downgrade reduces the braking denominator and lengthens stopping distance. Use the calculated result and the applicable project criteria as separate checks.
2. K-Value Design
The crest reference uses the 0.20 m object-height column. The sag reference is for driver comfort. Check actual visibility and vertical alignment separately.
3. Verify Available Sight Distance
Check the vehicle path, curve length and obstructions in the actual alignment before selecting a setback.
Stopping & Passing Sight Distance Calculator Documentation
Technical specifications, mathematical formulas, and civil guidelines
Select a listed design speed and enter longitudinal grade in percent. Use a negative value for a downgrade. The reaction time defaults to 2.5 s and can be adjusted.
For dry paved roads, the calculated SSD in metres is 0.278 Vt + V² / [254(f + g/100)]. V is in km/h, t is in seconds, and f is the friction factor for the selected speed from ERA Table 7-2.
At 80 km/h on a level road with a 2.5 s reaction time, the reaction and braking distances are 55.60 m and 82.61 m. The calculated SSD is 138.21 m. Separately, Table 7-2 lists 140 m level SSD and 545 m minimum passing distance.
The crest K reference uses the 0.20 m object column of Table 9-1. The sag K reference uses the driver-comfort column of Table 9-3. These are tabulated references. Check available visibility, road surface and governing project requirements before making an alignment or setback decision.
Source: ERA Geometric Design Manual 2013, §7.2 and Tables 7-2, 9-1 and 9-3.
Developer of InfraDigital CAD
Read the tool-specific source, assumptions and limits before interpreting its output. These browser-based tools are provided as productivity aids for preliminary engineering and drafting checks. Project-specific independent verification and approval by a licensed Professional Engineer (PE / REng) is required before final design submission, drawing stamping, or construction implementation.
Author: Yonatan Abrham
InfraDigital CAD developer
Technical Integrity & Independent Verification: Use the tool for the stated calculation or workflow. Check the applicable edition, input assumptions and limits in the tool documentation.
The user remains solely responsible for verifying that all inputs, soil parameters, traffic projections, and geometry comply with project-specific statutory requirements and geotechnical investigations prior to final engineering approval or construction stakeout.