The Transportation Planning Process: Evaluating Impacts

A part of the transportation planning process is evaluating impacts. In conventional transportation planning impacts usually quantified and considered include:

• Financial costs to governments
• Vehicle operating costs 
• Travel Time
• Per mile crash risk
• Projected construction environmental impacts

Conversely there are also many impacts that are overlooked during the process, some of those include:

• Parking costs
• Public fitness and health impacts
• Transportation diversity and equity impacts
• Traveler’s preferences for alternative modes
• Indirect environmental impacts
• Project construction traffic delays

Roadway Level-of-Service ratings are used in traditional transportation planning to evaluate traffic flow and plan for roadway improvements. The problem with this system is the lack of consideration for a myriad of other factors in transport. 

Roadway Level-of-Service

Level-of-Service	Description	Speed (mph)	Flow (veh./hour/lane)	Density (veh./mile)
A	Traffic flows at or above posted speed limit. Motorists have complete mobility between lanes.	Over 60	Under 700	Under 12
B	Slightly congested, with some impingement of maneuverability. Two motorists might be forced to drive side by side, limiting lane changes.	57-60	700-1,100	12-20
C	Ability to pass or change lanes is not assured. Most experienced drivers are comfortable and posted speed is maintained but roads are close to capacity. This is the target LOS for most urban highways.	54-57	1,100-1,550	20-30
D	Typical of an urban highway during commuting hours. Speeds are somewhat reduced, motorists are hemmed in by other cars and trucks.	46-54	1,550-1,850	30-42
E	Flow becomes irregular and speed varies rapidly, but rarely reaches the posted limit. On highways this is consistent with a road over its designed capacity.	30-46	1,850-2,000	42-67
F	Flow is forced, with frequent drops in speed to nearly zero mph. Travel time is unpredictable.	Under 30	Unstable	67-Maximum

Transportation planners have begun to apply Level-of-Service ratings, historically and typically used to rate roadways for automobile travel, to walking, cycling, and public transit. They also are considering transport demand management strategies, including multi-modal transportation, as alternatives to highway expansions, which were the usual response to traffic congestion.

Source: Introduction to Multi-Modal Transportation Planning, Victoria Transport Policy Institute. 2012