APPROACHVALUES  EXCLUSIVE LEFT TURN SHARED LEFTAND THRU  EXCLUSIVE THRU LANE SHARED THRUAND RIGHT  EXCLUSIVE RIGHT TURN TOTALS TRAFFIC INTERSECTION CAPACITY CALCULATOR Measurement: "spd" "len" mi/hr, ft  ft/s, ft  Km/hr, m  m/s, m Intersection Type: Free flow   Signal      All Stop    Stop Sign Number of Lanes # of Lanes # of Lanes # of Lanes # of Lanes # of Lanes Total Lanes Lane Width Width "len" Width "len" Width "len" Width "len" Width "len" Total "len" 85 Percentile Speed Speed "spd" Speed "spd" Speed "spd" Speed "spd" Speed "spd" Heavy Vehicle Portion Heavy Part Heavy Part Heavy Part Heavy Part Heavy Part Signal Green Portion Green Part Green Part Green Part Green Part Green Part Conflict veh/hr Confl vh/hr Confl vh/hr Confl vh/hr Confl vh/hr Confl vh/hr Street Data Park  Left Turn Part ONE WAY Turn Part Park  Right Group Capacity veh/hr Group vh/hr Group vh/hr Group vh/hr Group vh/hr Group vh/hr Total vh/hr Lane Capacity veh/hr Lane vh/hr Lane vh/hr Lane vh/hr Lane vh/hr Lane vh/hr Avg vh/hr Avg Headway s/veh Space s/veh Space s/veh Space s/veh Space s/veh Space s/veh Space s/veh

# OPERATION

### Philosophy:

This calculator is different from the others, because it never gives a capacity that requires drivers to violate safe following distances.

### The Controls:

• Measurement:

Sets which units of measure are used for the input values of speed (spd) and length (len). Four settings are possible:

• Miles per hour, and feet
• Feet per second, and feet
• Kilometers per hour, and meters
• Meters per second, and meters

Note: Changing this setting does not change any numbers already entered as speeds or distances to converted values. Instead, the entered values are now changed to be in the new measurements.

• Intersection Type:

Sets the kind of intersection the capacity is calculated for.

• Free Flow - No intersection or intersection where the cross road stops.
• Signal - Intersection controlled by a traffic signal.
• All Stop - The intersection is an All-Way Stop.
• Stop Sign - The approach has to stop for the cross road.

Note: The effects of each setting are covered separately for each variable.

• CALCULATE

Calculates the values of capacity, lane capacity, and headway.

• ERASE ALL

Clears all values in the grid to zero.

• The Columns:
• EXCLUSIVE LEFT TURN - Lanes used exclusively for left turns
• SHARED LEFT AND THRU - Lane shared between left turn and thru - Use this for a single lane approach
• EXCLUSIVE THRU LANE - Lane used exclusively for straight ahead traffic
• SHARED THRU AND RIGHT - Lane shared between right turn and thru
• EXCLUSIVE RIGHT TURN - Lane used exclusively for right turn
• Number of Lanes

Enter the number of lanes on the approach for each type of lane. Note that there can be only one shared lane of each kind.

• Lane Width

Enter the width of a lane for each type of lane. Uses the "wid" setting in Measurement to select the units.

• 85 Percentile Speed

Enter the speed for each type of lane. Uses the "spd" setting in Measurement to select the units.

• Heavy Vehicle Portion

Enter a value between 0 and 1 denoting the portion of traffic in the selected lane that consists of heavy vehicles. For example, 0.25 denotes that 1/4 of the traffic on the lane is truck traffic.

• Signal Green Portion

Enter the portion of time the signal is green for the selected lane(s). For example, a value of .6 means the signal is green 60% of the time. Used only when the intersection type is Signal.

• Conflict veh/hr

Number of vehicles moving in conflict with each lane type:

• For a Free Flow intersection, enter the number of vehicles per hour in conflict with left turns in the spaces for both kinds of left turn lanes. Not used by the thru and right movement columns.
• For a Signal intersection, enter the number of vehicles per hour that are in conflict with permissive left turns. Enter zero if the left turns are exclusively protected. Not used for thru and right movements.
• For an All Stop intersection, sum up the total number of vehicles per hour of all movements that are in conflict with the movement for the lane selected, and enter the sum. For combined lanes or single lane approaches, include all movements in conflict with all movements in the lane.
• For a Stop Sign intersection, sum up the total number of vehicles per hour of all movements that are in conflict with the movement for the lane selected, and enter the sum. For combined lanes or single lane approaches, include all movements in conflict with all movements in the lane.
• Park Left

Check if parking is allowed in a parking lane to the immediate left of the leftmost active lane in the grid. Used only for one-way streets and streets allowing parking next to the median.

• Park Right

Check if parking is allowed in a parking lane to the right of the rightmost active lane in the grid.

• Turn Part

For lanes with more than one movement, enter the portion of traffic expecting to make turns.

• One Way

Check the box if the approach is one way with no oncoming traffic conflicting with left turns.

### Results:

• Group Capacity veh/hr

Gives the capacity in vehicles per hour for the entire group of lanes in the column.

The total at the right is the total for the entire approach.

• Lane Capacity veh/hr

Gives the capacity in vehicles per hour for each lane in the group of lanes in the column.

The average at the right is the average traffic per lane for the entire approach.

Note that if the parking checkbox is checked, the 500 veh/hr would be removed from the right lane, but this calculation spreads it among more than one lane in the group.