diff --git a/src/aspen/delay_calculation.rs b/src/aspen/delay_calculation.rs
new file mode 100644
index 00000000..e69de29b
diff --git a/src/aspen/lib.rs b/src/aspen/lib.rs
index b5216930..62448399 100644
--- a/src/aspen/lib.rs
+++ b/src/aspen/lib.rs
@@ -14,6 +14,7 @@ use std::collections::HashMap;
 use std::net::IpAddr;
 use std::net::SocketAddr;
 use tarpc::{client, tokio_serde::formats::Bincode};
+pub mod rt_recent_history;
 
 #[derive(serde::Deserialize, Clone, serde::Serialize, Debug)]
 pub struct TripsSelectionResponse {
diff --git a/src/lib.rs b/src/lib.rs
index be781b4b..70b0719f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -65,6 +65,7 @@ use std::hash::Hash;
 use std::hash::Hasher;
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 pub mod metrolink_ptc_to_stop_id;
+pub mod rt_recent_history;
 
 #[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq, Hash)]
 pub struct ChateauDataNoGeometry {
@@ -897,3 +898,4 @@ mod test_calendar {
         };
     }
 }
+
diff --git a/src/rt_recent_history/mod.rs b/src/rt_recent_history/mod.rs
new file mode 100644
index 00000000..f8c1d67d
--- /dev/null
+++ b/src/rt_recent_history/mod.rs
@@ -0,0 +1,14 @@
+use crate::aspen_dataset::AspenStopTimeEvent;
+
+pub struct RtKey {
+    pub trip_id: Option<String>,
+    pub route_id: Option<String>,
+    pub direction_id: Option<u32>,
+    pub start_time_secs: Option<u32>,
+    pub start_date: Option<chrono::NaiveDate>
+}
+
+pub struct RtCacheEntry {
+    pub last_updated: chrono::DateTime<chrono::Utc>,
+    pub events: Vec<AspenStopTimeEvent>
+}
\ No newline at end of file